Human Sexuality
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Discovering Human Sexuality THIRD EDITION
Available free of charge, this online companion to the textbook provides a thorough set of study tools that includes questions, activities, flashcards, and other
resources to help you learn the material quickly and effectively.
Animations (included in the Activities) clearly explain important concepts and processes in easy-to-follow narratives.
A comprehensive set of Study Questions covers the full range of content in every chapter. Each
question is referenced to a textbook section, for review.
Labeling Activities and dynamic step-by-step illustrations simplify complex concepts and reinforce
important anatomy and terminology.
Companion Website
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http://sites.sinauer.com/discoveringhumansexuality3e
WEB ACTIVITIES The following activities are available on the site.
Page numbers indicate where in the textbook each is referenced.
ADDITIonAL fEATurES Chapter outlines & Summaries provide a thorough review of each chapter.
Learning objectives in the form of short-answer questions help you focus on the important topics in each chapter.
Quizzes with multiple choice and essay questions allow you to test your comprehension of each chapter and synthesize and apply the concepts you have learned. (Instructors must register in order for their students to be able to take the quizzes.)
flashcards help you quickly learn and review all the important terminology introduced in each chapter.
In addition, the website includes a set of Web Links for each chapter, as well as a complete Glossary.
2.1 The Vulva . . . . . . . . . . . . . . . . . . 22
2.2 Internal Anatomy of the Vulva. . . . . . . . . . . . . . . . . . . . . . . . 29
2.3 The Female Reproductive Tract, Part 1. . . . . . . . . . . . . . . 30
2.4 The Female Reproductive Tract, Part 2. . . . . . . . . . . . . . . 30
2.5 The Pap Test. . . . . . . . . . . . . . 34
2.6 Ovarian and Uterine Cycles . . . . . . . . . . . . 38, 42, 43
2.7 Main Processes of the Menstrual Cycle . . . . . . . . . . 43
2.8 The Reproductive Years . . . . . . . . . . . . . . . . . . . . . . . 44
2.9 Internal Structure of the Lactating Breast. . . . . . . . . . 51
_____________________________________
3.1 The Male External Genitalia . . . . . . . . . . . . . . . . . . . 62
3.2 Internal Structure of the Erect Penis and the Urethra . . . . . . . . . . . . . . . . . . . . . 65
3.3 The Mechanism of Erection . . . . . . . . . . . . . . . . . . . . 69
3.4 The Scrotum and Its Contents. . . . . . . . . . . . . . . . . . . 71
3.5 Internal Structure of the Testicle and Epididymis. . . . . . . . . . . . . . . . . 73
3.6 The Male Reproductive Tract . . . . . . . . . . . . . . . . . . . . . . . . 74
3.7 Anatomy of the Prostate. . . . . . . . . . . . . . . . . . . . 76
_____________________________________
4.1 Development of the Male and Female Reproductive Tracts. . . . . . . . . . . . . . . . . . . . . . . 89
_____________________________________
7.1 Definitions of Sexual Relationships . . . . . . . . . . . 192
7.2 Sternberg’s Seven Types of Love . . . . . . . . . . . . . . . . . . . 209
_____________________________________
8.1 How a Home Pregnancy Test Works . . . . . . . . . . . . . . 229
8.2 In Vitro Fertilization. . . . . 232 _____________________________________
9.1 Vasectomy . . . . . . . . . . . . . . 291
9.2 Tubal Sterilization . . . . . . 292 _____________________________________
15.1 Milestones in the Global HIV/AIDS Pandemic . . . 480
_____________________________________
a.1 Mitosis . . . . . . . . . . . . . . . . . . . 552
a.2 Mitosis Time-Lapse Video . . . . . . . . . . . . . . . . . . . . . 552
a.3 Meiosis. . . . . . . . . . . . . . . . . . . 552
a.4 Differences and Similarities between Meiosis and Mitosis . . . . . . . . . . . . . . . . . . . 552
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Discovering Human Sexuality
third edition
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Sinauer Associates, Inc. Publishers Sunderland, Massachusetts U.S.A.
Discovering Human Sexuality
third edition
Simon LeVay west hollywood, california
Janice Baldwin university of california
santa barbara
John Baldwin university of california
santa barbara
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Discovering Human Sexuality, Third Edition Copyright © 2015 by Sinauer Associates, Inc. All rights reserved. This book may not be reproduced in whole or in part without permission from the publisher.
For information or to order, address: Sinauer Associates P.O. Box 407 Sunderland, MA 01375 USA Fax: 413-549-1118 E-mail: [email protected] Internet: www.sinauer.com
Library of Congress Cataloging-in-Publication Data
LeVay, Simon. Discovering human sexuality / Simon LeVay, West Hollywood, CA, Janice Baldwin, University of California, Santa Barbara, John Baldwin, University of California, Santa Barbara. — Third edition. pages cm ISBN 978-1-60535-275-6 (alk. paper) 1. Sex (Psychology) 2. Sex (Biology) 3. Sex–Social aspects. I. Baldwin, Janice I. II. Baldwin, John D., 1941- III. Title. BF692.L47 2015 306.7–dc23 2014044757
Printed in the USA 5 4 3 2 1
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mailto:[email protected]
http://www.sinauer.com
Simon LeVay, PhD is a British-born neuroscientist turned writer and teacher. He has served on the faculties of Harvard Medical School and the Salk Institute for Biologi- cal Studies and has taught at Harvard; the University of California, San Diego; and Stanford University. He is best known for a 1991 study that described a difference in brain structure between heterosexual and homosexual men; this study helped spark a wealth of new research on the biology of sexual orientation. LeVay is the author or coauthor of 11 books, the most recent of which is a historical novel, The Donation of Constantine (Lambourn, 2013).
Janice Baldwin, PhD and John Baldwin, PhD are sociologists at the University of California, Santa Barbara. They have been collaborators in numerous studies and coauthored many articles in the areas of play, creativity, sexuality, and sex educa- tion, as well as the textbook Behavior Principles in Everyday Life (Prentice Hall). John Baldwin’s latest book is Ending the Science Wars (Paradigm, 2008). The Baldwins co- teach an undergraduate human sexuality course that is regularly voted best course at UCSB. They also teach an advanced seminar course on the same topic. Their students run a sex-ed website, SexInfoOnline (www.SexInfoOnline.com).
About the Authors
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http://www.SexInfoOnline.com
chapter 1 Sexuality: Pathways to Understanding 3
chapter 2 Women’s Bodies 21
chapter 3 Men’s Bodies 61
chapter 4 Sex, Gender, and Transgender 87
chapter 5 Attraction, Arousal, and Response 123
chapter 6 Sexual Behavior 155
chapter 7 Sexual Relationships 191
chapter 8 Fertility, Pregnancy, and Childbirth 227
chapter 9 Contraception and Abortion 265
chapter 10 Sexuality across the Life Span: From Birth to Adolescence 305
chapter 11 Sexuality across the Life Span: Adulthood 335
chapter 12 Sexual Orientation 365
chapter 13 Atypical Sexuality 401
chapter 14 Sexual Disorders 431
chapter 15 Sexually Transmitted Infections 461
chapter 16 Sexual Assault, Harassment, and Partner Violence 493
chapter 17 Sex as a Commodity 523
appendix a Sex and Evolution 551
appendix b Sex and the Nervous System 573
Brief Contents
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Contents
Sexuality Is a Broader Concept than Sex 4
Studying Sexuality Has Practical Benefits 4
Sexuality Has Changed over Time 4 Sexuality has been influenced by evolution 5
Society has changed sexuality 5
Box 1.1 Meet My Dads 6
Marriage has been transformed 8
Sex has become a topic of social discourse 9
Social movements have affected sexuality 10
Box 1.2 Freud and Hirschfeld: Contrasting Theories on Sexual Orientation 11
Sexuality Can Be Studied with a Wide Variety of Methods 12
Biomedical research focuses on the underlying mechanisms of sex 12
Psychology includes diverse approaches to sexuality 13
Sociologists focus on the connection between sex and society 15
The economic approach weighs costs and benefits 16
Chapter 1 Sexuality: Pathways to Understanding 3
A Woman’s Vulva Includes Her Mons, Labia, Vaginal Opening, and Clitoris 22
There is more to the clitoris than meets the eye 24
Box 2.1 Female Genital Cutting 26
The appearance of the vaginal opening is variable 27
The Vagina Is the Outermost Portion of the Female Reproductive Tract 29
The vagina undergoes changes during arousal 31
The G-spot is a controversial erogenous zone 31
The Anus Can Also Be a Sex Organ 32
The Uterus Serves a Double Duty 32 Box 2.2 Genital Self-Examination 33
Cancer can affect the cervix or the endometrium 34
Other uterine conditions include fibroids, endometriosis, abnormal bleeding, and prolapse 35
Should hysterectomy be so common? 36
The Oviducts Are the Site of Fertilization 36
The Ovaries Produce Ova and Sex Hormones 37
Box 2.3 The Feedback Loop that Controls Female Hormone Production 38
Menstruation Is a Biological Process with Cultural and Practical Aspects 40
Box 2.4 Menstrual Synchrony: Reality or Myth? 41
The menstrual cycle has three phases 42
The cycle is driven by hormonal changes 43
Does the menstrual cycle influence sexuality? 44
Attitudes toward menstruation vary 44
Box 2.5 Attitudes toward Menstruation 45
Women use pads, tampons, or cups during menstruation 46
Menstrual Problems Are Common but Treatable 48
Menstrual pain may or may not reflect underlying pelvic disease 48
The premenstrual syndrome has physical and psychological aspects 48
Menstruation stops during pregnancy—and for many other reasons 49
Sex steroids affect systems in women besides the reproductive tract 50
The Breasts Have Both Erotic and Reproductive Significance 50
Chapter 2 Women’s Bodies 21
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x CONTENTS
Breast cancer mortality can be reduced 51
Many factors affect the risk of breast cancer 52
Early detection is important 54
Box 2.6 Breast Self-Examination 55
Treatment depends on the diagnostic findings and the woman’s choice 56
Most women with breast cancer return to an active sex life 56
The Male External Genitalia Are the Penis and Scrotum 62
The penis combines erotic, reproductive, and urinary functions 63
Box 3.1 Male Circumcision 64
Box 3.2 How Big Should a Penis Be? 67
Box 3.3 Diphallia 68
Penile Erection Involves Nerves, Blood, and Chemistry 68
Erection is filling of the penis with blood 69
Muscles are also involved in erection 70
Erections occur during sleep 70
The scrotum regulates the temperature of the testicles 70
The Testicles Produce Sperm and Sex Hormones 71
Other glands contribute secretions to the semen 73
What is semen? 74
Box 3.4 Disorders of the Testicles 75
Box 3.5 Disorders of the Prostate Gland 76
Ejaculation Requires Coordination of Muscles and Glands 77
The testicles secrete sex hormones 78
Box 3.6 Designer Steroids 80
The brain and pituitary gland regulate hormone levels 80
Nudity Is Culturally Regulated 81
Chapter 3 Men’s Bodies 61
Genes and Hormones Guide Sex Development 88
Female and male reproductive tracts develop from different precursors 88
Female and male external genitalia develop from the same precursors 89
The gonads descend during development 91
Puberty is sexual maturation 92
The brain also differentiates sexually 92
Sex Development May Go Awry 93 Chromosomal anomalies affect growth and fertility 93
The gonads or genitals may be sexually ambiguous 95
Box 4.1 My Life with Androgen Insensitivity Syndrome 96
Gender Is a Central Aspect of Personhood 97 Gender identity might not match anatomical sex 97
Women and men differ in a variety of cognitive and personality traits 98
There are Many Sex Differences in Sexuality 99
Many gender differences arise early in life 101
Biological Factors Influence Gender 102
Evolutionary forces act differently on females and males 102
Box 4.2 Gendered Play in Primates 103
Experiments demonstrate a role for sex hormones 103
Life Experiences Influence Gender 105 Gender is molded by socialization 105
Cognitive developmental models emphasize thought processes 108
Gender Development Is Interactive 108 Box 4.3 The Boy Who Was Raised as a Girl 109
Transgender People Cross Society’s Deepest Divide 110
Box 4.4 Trans Men and Women in Cross- Cultural Perspective 111
Transexual individuals are of more than one kind 112
Changing sex is a multistage process 113
Some transgender people do not want surgery 115
Box 4.5 How Should We Treat Gender- Dysphoric Children? 116
Trans people struggle for awareness and acceptance 118
Chapter 4 Sex, Gender, and Transgender 87
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CONTENTS xI
Sexual Attraction: It Takes Two 124 Beauty is not entirely in the eye of the beholder 124
Culture influences the attractiveness of bodies 126
Attractiveness involves senses besides vision 129
Behavior and personality influence sexual attractiveness 130
Box 5.1 Sex Pheromones 131
Familiarity may increase or decrease attraction 133
Perceived attractiveness varies around the menstrual cycle 135
Judgments of attractiveness change as people get to know each other 136
Asexual women and men do not experience sexual attraction 136
Sexual Arousal Has Multiple Roots 137 Fantasy is a common mode of sexual arousal 138
Arousal occurs in response to a partner 139
Hormones influence sexual arousability 140
Conditioning may influence arousal 141
Box 5.2 Aphrodisiacs and Drugs 142
Sexual Arousal Follows a Response Cycle 143
In the excitement phase, genital responses begin 143
In the plateau phase, arousal is maintained 144
Orgasm is the climax of sexual arousal 145
Box 5.3 Female Ejaculation 146
Brain imaging suggests where orgasm may be experienced 147
Box 5.4 Foot Orgasms 148
In the resolution phase, arousal subsides 149
The phases may be linked in different ways 149
Some people experience multiple orgasms 150
Men experience a refractory period 151
The Masters and Johnson cycle may be incomplete 151
Chapter 5 Attraction, Arousal, and Response 123
People Derive Pleasure from Diverse Sexual Behaviors 156
Masturbation Is a Very Common Form of Sexual Expression 156
Box 6.1 Sex and Happiness 157
Negative attitudes toward masturbation are still prevalent 158
Several demographic factors influence masturbation 158
Women use more diverse techniques of masturbation than men 160
Gay people masturbate more than heterosexuals 161
Different cultures have different attitudes toward masturbation 161
The Kiss Represents True Love— Sometimes 162
Sexual Touching Takes Many Forms 163
Oral Sex Is Increasingly Popular 164 Fellatio is oral stimulation of the penis 164
Cunnilingus is oral stimulation of the vulva 165
Most Heterosexual Sex Includes Coitus 166 Coitus can be performed in many different
positions 166
The man-above position is a traditional favorite 167
The women’s movement encouraged alternative positions 168
Box 6.2 Progress in Coitus Research 169
Box 6.3 Sex and the Seasons 171
Anal Sex May Be a Part of Either Heterosexual or Male Homosexual Behavior 172
Men and Women May Have Different Preferences for Sexual Encounters 173
Sex Toys Are Used to Enhance Sexual Pleasure 174
Sex May Be in Groups 177 Box 6.4 What Is “Great Sex”? 178
Sexual Behavior and Attitudes Vary among Cultures 179
The Kama Sutra is the classic work on how to make love 179
The Aka emphasize the importance of frequent sex 181
Many Disabled People Have Active Sex Lives 181
Box 6.5 On Seeing a Sex Surrogate 182
Many intellectually disabled people are competent to make sexual choices 183
Spinal cord injuries present a major challenge to sexual expression 184
Arthritis is the number one disability affecting sex 186
Chapter 6 Sexual Behavior 155
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xII CONTENTS
Sexual Relationships Are Motivated by Many Factors 192
Moral Judgments about Sex Depend on Its Context 192
Demographic factors affect sexual attitudes 192
Box 7.1 Who May Marry? 194
Americans’ Attitudes Have Changed over Time 195
Casual Sex Has More Appeal to Men than to Women 196
Hooking up—the new norm? 196
Box 7.2 Straight Women, Gay Sex 197
Hookups can be pleasurable or abusive 198
Hookups can have positive or negative consequences 200
Casual sex is more accepted in the gay male community 200
Negotiating sex involves flirting 201
Box 7.3 Flirting Styles 202
Non-Cohabiting Relationships Are Often Short-Lived 203
Same-sex relationships have their own scripts 205
Non-cohabiting relationships may evolve rapidly 205
Love Cements Many Sexual Relationships 206
There are different kinds of love 206
Being in love may be the justification for marriage or sex 206
Liking and reciprocal attraction precede falling in love 206
Researchers are probing the biological basis of love 207
One theory proposes that love has three components 208
Unrequited Love Is Painful for Both Parties 210
Box 7.4 Love Stories 211
The rejector may experience guilt 212
Life Experiences Mold Our Sexual Relationships 213
Relationship styles are influenced by childhood attachments 213
Couples in relationships resemble each other 213
Communication Is a Key Factor in the Success of Relationships 214
Communication may be inhibited by upbringing or by the gender barrier 214
Relationship and marriage education teaches communication skills 215
How couples deal with conflict affects the stability of their relationship 216
Love, Jealousy, and Infidelity Are Intertwined 218
Jealousy can have a positive function 218
Extra-Pair Relationships Have Many Styles and Motivations 219
Personal and evolutionary factors influence infidelity 220
Box 7.5 We Just Clicked 221
Extra-pair relationships are uncommon 222
Chapter 7 Sexual Relationships 191
Pregnancy and Childbirth Raise Major Health Concerns 228
Pregnancy Is Confirmed by Hormonal Tests 228
Box 8.1 Birth Facts 229
Infertility Can Result from a Problem in the Woman or in the Man 230
A variety of factors can reduce sperm counts 230
Box 8.2 Declining Sperm Counts? 231
In vitro fertilization can circumvent many sperm problems 232
Box 8.3 Choosing Children’s Sex 234
Sperm can be donated 235
Abnormalities of the female reproductive tract may reduce fertility 236
Failure to ovulate can be dealt with by drugs or by egg donation 236
Surrogate mothers bear children for others 236
Adoption is limited by the supply of healthy infants 237
Fertility declines with age 237
Many Embryos Do Not Survive 239 Rh factor incompatibility can threaten second
pregnancies 239
Ectopic pregnancy can endanger the mother’s life 239
Chapter 8 Fertility, Pregnancy, and Childbirth 227
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CONTENTS xIII
Pregnancy Is Conventionally Divided into Three Trimesters 240
The First Trimester Is a Period of Major Changes 240
Prenatal care provides health screening, education, and support 242
Adequate nutrition is vital to a successful pregnancy 242
Tobacco, alcohol, drugs, and radiation can harm the fetus 243
The Second Trimester Is the Easiest 245 Tests can detect fetal abnormalities 245
Sex during pregnancy is healthy 247
Moderate exercise during pregnancy is beneficial 248
The Third Trimester Is a Time of Preparation 248
A hospital is the best location for childbirth if complications are foreseen 249
Childbirth classes prepare parents for birth 249
The fetus also makes preparations for birth 250
Labor Has Three Stages 251
The first stage of labor is marked by uterine contractions and cervical dilation 251
Box 8.4 Pain-free Childbirth 253
The second stage is the delivery of the baby 254
The newborn child adapts quickly 255
The third stage is the expulsion of the placenta 255
Box 8.5 Cesarean Section 256
Premature or delayed birth is hazardous 256
The Period after Birth Places Many Demands on Parents 257
Postpartum depression may be accompanied by disordered thinking 258
Childbirth and parenthood affect sexuality 258
Breast-Feeding Is the Preferred Method of Nourishing the Infant 259
Lactation is orchestrated by hormones 259
The content of breast milk changes over time 259
Infant formula is an alternative to breast milk 260
Breast-feeding has many advantages and some drawbacks 260
Birth Control Has a Long History 266 Feminists led the campaign to legalize
contraception 266
Box 9.1 Margaret Sanger and the Birth Control Movement 267
Contraception has not yet solved the problem of unintended pregnancy 268
Different users have different contraceptive needs 268
Physical Methods Block Sperm Transport 270
Male condoms are reliable when properly used 270
Female condoms are relatively intrusive 272
Box 9.2 Male Contraceptives of the Future? 273
Diaphragms and cervical caps are inconvenient but have few side effects 274
Spermicides are not very reliable when used alone 275
Intrauterine devices require little attention 276
Hormone-Based Methods Are Easy to Use 277
Combination pills offer health benefits 278
Continuous use of combination pills eliminates menstrual periods 280
Progestin-only pills have fewer side effects 281
Hormones Can Be Administered by Non-Oral Routes 282
Depo-Provera lasts three months 282
Transdermal patches last a week 283
Vaginal rings last three weeks 284
Implants are extremely reliable 285
Behavioral Methods Can Be Demanding 285 In fertility awareness methods, couples avoid coitus
during the fertile window 285
The withdrawal method is simple but challenging 287
Noncoital sex can be used as a means of avoiding pregnancy 288
There Are Contraceptive Options after Unprotected Coitus 289
Sterilization Is Highly Reliable 290 Vasectomy is a brief outpatient procedure 290
Tubal sterilization is more invasive and expensive 292
Disabled Persons Have Special Contraceptive Needs 293
Several Safe Abortion Procedures Are Available 293
Chapter 9 Contraception and Abortion 265
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xIV CONTENTS
Box 9.3 Abortion in the United States: Key Statistics 294
Vacuum aspiration is the standard first-trimester surgical method 295
Dilation and evacuation is used early in the second trimester 295
Induced labor and hysterotomy are performed late in the second trimester 296
Medical abortions are two-step procedures 296
Abortions do not cause long-lasting ill effects 297
Box 9.4 Does Abortion Traumatize Women? 298
Americans Are Divided on Abortion, but Most Favor Restricted Availability 298
The availability of abortion is decreasing 299
Box 9.5 Feticide 301
Some Forms of Childhood Sexual Expression Are Common 306
Primates display sexual behavior early in life 306
In contemporary Western culture, children are insulated from sex 306
Some children engage in solitary sexual activity 307
Box 10.1 Talking with Children about Sex 308
Sex with others can occur during childhood 309
Cultures vary in their attitudes toward childhood sexuality 310
Some Children Have Sexual Contacts with Adults 311
Most adult-child contacts involve older children and are single encounters 311
Some kinds of adult-child sex are more harmful than others 311
Strategies to prevent adult-child sex are quite effective 312
Box 10.2 Sex and Suggestibility 313
Preadolescence May Be Marked by an Increase in Sexual Interest 314
Preadolescent children segregate by sex 314
Strict gender norms may traumatize children who become gay adults 314
Puberty Is a Period of Rapid Maturation 315 Puberty is marked by visible and invisible changes 315
Box 10.3 My First Period 317
Puberty occurs earlier in girls than boys 318
What drives puberty? 319
The body signals its readiness for puberty to the brain 320
Puberty may come too early or too late 321
Adolescence Is a Time of Sexual Exploration 322
Many cultures have puberty rites 322
There are social influences on teen sexual behavior 323
Social media have risks and benefits 324
Males masturbate more than females 325
The sexual behavior of American teens has increased and diversified 326
Box 10.4 Losing It 327
Noncoital sex is popular among teens 328
Teen Sexuality Is Central to Identity Development 329
Teen relationships are often short-lived 330
Teen pregnancy is declining but is still too common 330
Chapter 10 Sexuality across the Life Span: From Birth to Adolescence 305
In Young Adulthood, Conflicting Demands Influence Sexual Expression 336
Most young men and women have only a few sex partners 336
Cohabitation Is an Increasingly Prevalent Lifestyle 337
Box 11.1 Cohabitation: Laws in Conflict 337
Cohabitation has diverse meanings 338
Cohabitation does not harm a subsequent marriage 339
Chapter 11 Sexuality across the Life Span: Adulthood 335
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CONTENTS xV
Marriage Takes Diverse Forms 339 The formalization of sexual unions has social
and personal functions 340
Many societies have permitted polygamy 340
Box 11.2 Mormon Polygamy 341
Polyamory includes a variety of nonmonogamous relationships 342
The Institution of Marriage Is Evolving 343 Box 11.3 Extreme Marriages 344
Companionate marriage makes the availability of divorce a necessity 344
Marriage is becoming a minority status 345
Relationship options have diversified 345
Most Long-Term Couples Are Satisfied with Their Sex Lives 346
The frequency of sex declines in the course of long-term relationships 347
Marital satisfaction declines during middle age 348
Many Factors Bring Relationships to an End 348
Box 11.4 You Know the Future of Your Marriage 349
Dissimilarity between husbands and wives shortens marriages 350
Marital Disruption Can Have Negative and Positive Consequences 351
Divorced men and women can suffer psychological, physical, and economic damage 351
Divorce may be the start of a new life 351
Many divorced people remarry 352
Does marriage have a future? 352
Menopause Marks Women’s Transition to Infertility 353
Menopause may be caused by depletion of ova 354
Women may experience a decline in sexual desire at menopause 354
Decreased hormone levels affect a woman’s physiology 355
Hormone therapy can reduce menopausal symptoms 355
Ethnicity influences the experience of menopause 356
Men’s Fertility Declines Gradually with Age 357
The Sex Lives of Old People Have Traditionally Been Ignored 357
Aging is accompanied by physiological changes in the sexual response 359
Medical conditions, drugs, and social factors can impair the sexuality of older people 359
Box 11.5 Seniors on Sex 360
The experience of aging affects people in diverse ways 360
There Is a Spectrum of Sexual Orientations 366
Sexual Orientation Is Not an Isolated Trait 367
Diverse Theories Attempt to Explain Sexual Orientation 368
Box 12.1 Boys Will Be Girls 369
Freud proposed psychodynamic models 370
Sexual orientation has been attributed to socialization 370
Biological theories focus on prenatal hormones and genes 371
Box 12.2 Why Gay Genes? 374
The Gay Community Has Struggled for Equal Rights 375
The gay rights movement began in Germany 375
Box 12.3 Gay Martyrs 376
Gay rights are a global issue 377
Growing Up Gay Presents Challenges 379 Box 12.4 Global Perspectives on Sexual Orientation 380
Box 12.5 Gay and Homeless 381
Coming out is a lifelong process 382
Lesbians and gay men are well represented in certain occupations 383
Gay People Who Belong to Minorities Have Special Concerns 384
Gay Sex Has Its Own Style 385 There is diversity within the gay community 386
Some gay people are parents 387
Changing One’s Sexual Orientation Is Difficult or Impossible 388
Homophobia Has Multiple Roots 389
Chapter 12 Sexual Orientation 365
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xVI CONTENTS
Cultural indoctrination transmits homophobia across generations 390
Gays are seen as rule breakers 391
Overcoming homophobia is a grassroots enterprise 392
Bisexual People Are Caught between Two Worlds 393
The prevalence of bisexuality depends on definitions 393
Bisexual people face prejudice 395
Lesbian, gay, straight, bi, other—more alike than different 396
Sexual Variety Is the Spice of Life 402 Most fetishes are related to the body 402
Box 13.1 Rubber Fetishism and the Internet 405
People cross-dress for a variety of reasons 406
Some men are aroused by trans women 407
Sadomasochism involves the infliction or receipt of pain or degradation 407
Box 13.2 In the Dungeon 409
Adult babies reenact infancy 410
Paraphilic Disorders Cause Distress or Harm Others 410
Exhibitionists expose themselves to nonconsenting persons 412
Obscene telephone calling is related to exhibitionism 413
Voyeurs are aroused by watching others 413
Frotteurism involves surreptitious physical contact 414
Some Adults Are Sexually Attracted to Children 414
Box 13.3 Frotteurism on Public Transit 415
Pedophilia and child molestation are not synonymous 415
Child molestation is a behavioral and legal term 417
Priests and others may molest children under their care 417
Some organizations support “minor-attracted people” 418
A Variety of Other Paraphilic Disorders Exist 418
Zoophiles are sexually attracted to animals 418
In necrophilia, nonresistance of the partner may be arousing 419
Sexual violence can be paraphilic 420
Box 13.4 Autoerotic Asphyxia 421
Sex Offenders Do Not Necessarily Repeat Their Offenses 422
There Are Numerous Theories of Paraphilic Disorders 422
Theories of Causation Have Suggested a Variety of Treatments 424
Conditioning is intended to change sexual desires 425
Cognitive therapy is aimed at preventing repeat offenses 425
The efficacy of psychological treatments is doubtful 426
Drug treatments interact with neurotransmitters or hormones 426
Castration is a treatment of last resort 427
Few “Kinks” Are Disorders 428
Chapter 13 Atypical Sexuality 401
Sexual Disorders Are Common 432 Men’s and women’s sexual problems differ 432
A multidisciplinary approach to treatment is preferred 432
Premature Ejaculation Is Men’s Number One Sex Problem 433
Box 14.1 Sensate Focus 434
There are different kinds of premature ejaculation 435
Sex therapy may help men to regulate excitation 436
Drug treatment may be effective 437
There Are Multiple Causes for Delayed Ejaculation 437
Erectile Disorder Has Many Causes and Treatments 438
Erectile disorder can have physical or psychological causes 438
Simple measures may alleviate the problem 439
Psychological treatments may be useful 439
Chapter 14 Sexual Disorders 431
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CONTENTS xVII
Viagra and similar drugs have become the leading treatments 440
Erectile disorder can be treated with devices and implants 441
Men May Have Little Interest in Sex 442
Sexual Pain Is Uncommon in Men 443
Female Sexual Arousal Disorder Involves Insufficient Genital Response 443
There Are Many Reasons for Sexual Pain in Women 444
Vaginismus may make intercourse impossible 445
Box 14.2 Dyspareunia: A Case History 446
Difficulty in Reaching Orgasm Is Common among Women 447
Psychotherapy and directed masturbation may be helpful 447
Box 14.3 Kegel Exercises 449
Faked orgasms offer a questionable solution 450
Too Much Interest in Sex Can Cause Problems 450
Compulsive sexual behavior can often be treated with SSRIs 451
Lack of Desire for Sex Is Not Necessarily a Problem 452
Estrogen or androgen treatment may improve sexual desire in women 452
Box 14.4 Sexual Minorities and Sexual Disorders 453
Sex therapy may be helpful for low sexual desire in women 454
New views on women’s response cycles may influence treatment options 455
Venereal Diseases Were Seen as Punishment for Sexual License 462
STIs Are Still Major Problems in the United States 462
Lice and Mites Are More of an Annoyance Than a Danger 465
Pubic lice itch, and that’s all they do 465
Scabies may be transmitted sexually or nonsexually 466
Trichomoniasis Is Caused by a Protozoan 467
Bacterial STIs Can Usually Be Treated with Antibiotics 467
Syphilis Is Down but Not Out 467 Untreated syphilis progresses through three stages 468
Syphilis has resisted elimination 469
Gonorrhea Can Lead to Infertility 469 Box 15.1 The Tuskegee Syphilis Study 470
Chlamydia Causes a Common Infection with Serious Complications 471
The Status of Bacterial Vaginosis as an STI Is Uncertain 473
Urethritis Can Be Caused by a Variety of Organisms 473
Viral STIs Can Be Dangerous and Hard to Treat 474
Molluscum Contagiosum Is a Self-Limiting Condition 474
Genital Herpes Is a Lifelong but Not Life- Threatening Infection 474
Recurrent outbreaks are the rule 475
Drug treatment can shorten or prevent outbreaks 476
Human Papillomaviruses Can Cause Genital Warts—and Cancer 477
HPV vaccines are available 478
Hepatitis Viruses Can Be Sexually Transmitted 479
AIDS Is Caused by the Human Immuno- deficiency Virus 479
Sexual transmission is chiefly by coitus and anal sex 481
HIV infection progresses in a characteristic way 482
Antiretroviral drugs suppress but don’t eliminate HIV 482
You Can Reduce Your STI Risks 484 Abstinence prevents STIs 484
Sexually active people can reduce their risk of STIs 485
Some sexual behaviors are riskier than others for STI transmission 485
Box 15.2 STIs and the Law 486
Condoms are the mainstay of STI prevention 487
Not Everything Is an STI 487
Chapter 15 Sexually Transmitted Infections 461
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xVIII CONTENTS
Can Money Buy You Love? 524 Historically, prostitution was viewed as a necessary
evil 524
Prostitution is on the decline 524
Box 17.1 Courtesans 525
There Is a Hierarchy of Prostitution 526 Street prostitution has many risks 526
Box 17.2 The Economics of Prostitution 527
Female, male, and transgender streetwalkers have different experiences 528
Some prostitutes work out of massage parlors and strip clubs 529
Escort services are the main form of prostitution in the United States 530
Only a minority of men use prostitutes 532
Some women use male prostitutes 532
Juvenile prostitution is of special concern 532
Box 17.3 Juvenile Prostitutes in Portland, Oregon 533
Sex trafficking is a global business 534
There Are Conflicting Views on Prostitution 536
There are several options for legal reform 537
There Is More to Sex Work than Prostitution 538
Stripping is going mainstream 538
Phone sex has diversified 539
Pornography Has Always Been Part of Human Culture 539
Pornography has battled censorship 540
New technologies mean new kinds of pornography 540
Box 17.4 What’s It Like to Be a Porn Star? 542
Chapter 17 Sex as a Commodity 523
What Is Rape? 494 Young women are the most frequent victims of rape 494
Most rapes are not reported 495
Most perpetrators are men known to the victims 495
College Rapes Are Becoming Less Common 496
Box 16.1 It Happened to Me 497
The number one “date rape drug” is alcohol 499
Rape Can Have Severe Effects on the Victim 500
Box 16.2 Reducing the Risk of Rape 501
Services are available for rape victims 501
Rape can inflict long-lasting harm 502
Box 16.3 Ten Ways Men Can Prevent Sexual Violence 503
Male victims have special concerns 504
LGBT people are at high risk 505
Rape Laws Have Become More Protective of Victims 506
Reforms began in the 1970s 506
What happens to men who rape? 506
Repeat offending is common 507
Why Do Men Rape? 508 Rape may have evolutionary roots 508
Some characteristics distinguish rapists from nonrapists 508
Social forces influence the likelihood of rape 509
Intervention Programs Are of Uncertain Value 509
Box 16.4 Rape and War 510
Intimate Partner Violence Is a Crime with Many Names 511
Intimate partner violence follows an escalating cycle 513
Breaking up is hard to do 513
Help is available 514
Sexual Harassment Occurs in Many Environments 514
There are two kinds of workplace sexual harassment 515
Sexual harassment often begins early 516
Sexual harassment harms its victims 517
Victims of sexual harassment can take steps to end it 517
There Are Three Kinds of Stalkers 518
Chapter 16 Sexual Assault, Harassment, and Partner Violence 493
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CONTENTS xIx
There is some pornography for women 543
There Are Conflicting Perspectives on the Value or Harm of Pornography 544
Research has not resolved the question of pornography’s effects 545
Sex Is Part of the Mass Media 546 Sex sells, sometimes 546
Rival Theories Offer Explanations for Sexual Reproduction 552
Sexual reproduction may remove harmful mutations 553
Sexual reproduction may generate beneficial gene combinations 554
Future research may solve the puzzle 554
Why Are There Two Sexes? 555 Hermaphrodites combine male and female reproductive
functions 556
Evolution Has Led to Diverse Methods of Sex Determination 556
In mammals, sex is determined by chromosomes 557
Sexual Selection Produces Anatomical and Behavioral Differences between Males and Females 557
Males and females follow different reproductive strategies 557
Females and males are exposed to different reproductive risks 558
Males often compete for access to females 558
Females often choose among males 559
Sometimes males make significant investments in reproduction 562
If males invest, sexual selection may work differently 562
Diverse Relationship Styles Have Evolved 563
Social and sexual arrangements are not necessarily the same 563
Male promiscuity offers obvious evolutionary benefits 564
Why are females promiscuous? 564
Female promiscuity leads to adaptive responses by males 565
Males may copulate with females by force 566
Sometimes, Helping Relatives Reproduce Is a Good Strategy 567
Avoiding Incest Is an Evolved Behavior 568
Sex Has Acquired Other Functions beyond Reproduction 568
Female and male bonobos engage in nonreproductive sex 568
Bonobos use sex for conflict resolution and alliance formation 569
Appendix A Sex and Evolution 551
Box B.1 The Nervous System 574
Erection Can Be Mediated by a Spinal Reflex 576
Sensory innervation of the genitalia 577
The pudendal and pelvic nerves 577
Erectile Tissue Forms a Hydraulic System 578
Muscles Are Also Involved in Erection 579
The Brain Influences Erection and Ejaculation 580
Appendix B Sex and the Nervous System 573
Glossary 583
Photo Credits 595
References 597
Author Index 631
Subject Index 635
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Preface
This past year was tough, making the switch to LeVay et al., but I’m glad I did it. Discovering Human Sexuality is unique in both approach and content. The authors have a point of view, but still provide balanced coverage of contro- versial issues. The boxes are wonderful. One of the things I like about it is the inclusion of historical and cross-cultural detail in the boxes. It’s a very readable and beautiful book. The illustrations and diagrams are excellent—the best of any text I have ever used.
Josephine Caldwell-Ryan Southern Methodist University
Discovering Human Sexuality, Third Edition, is the continuation of a textbook that originated in 2003 with the publication of Human Sexuality by Simon LeVay and Sharon Valente. Since then, the book has gone through several changes of author- ship, format, and title. One consistency, however, has been the identity of the lead author. Another has been the book’s high academic and pedagogical standards, which have earned it a prominent place in the market and broad praise from review- ers and users, including the kind words cited above.
The Second Edition of Human Sexuality appeared in 2006 with the same two authors. For the 2009 edition, however, Janice Baldwin replaced Sharon Valente. Also, we decided to produce two distinct versions of the book. One of them— Human Sexuality, Third Edition—continued the approach pioneered in the earlier editions. The other, which we titled Discovering Human Sexuality, was a somewhat shorter and more accessible version that demanded less prior knowledge on the part of the students, especially in the area of biol- ogy. John Baldwin joined LeVay and Janice Baldwin as third author of this version. In 2012 we continued with the same two versions (Human Sexuality, Fourth Edition, and Discover- ing Human Sexuality, Second Edition).
For the current edition we have decided to merge the two versions into one, which we have titled Discovering Human Sexuality, Third Edition. It was a difficult decision to make because both versions had been successful in the market- place and each served a somewhat different need. However, the workload involved in producing two different textbooks at the same time was excessive. In addition, we realized that we could incorporate the best features of Human Sexuality into Discovering Human Sexuality by judicious changes to the text and by the addition of two appendices containing more advanced “optional” material.
Features of Discovering Human Sexuality, Third Edition Important features of Discovering Human Sexuality distin- guish our book from competing texts:
evidence-based approach We believe that human sexu- ality is an academic subject like any other, meaning that it should be grounded in reason. Throughout the book, we have sought to present statements that are supported by data, ideas that are tested or testable, and recommendations that are based on research. There are many unanswered questions in sexuality, of course—questions about how ab- normal modes of sexual expression (paraphilic disorders) develop, for example, and how best to treat them. In deal- ing with these controversies, an evidence-based approach demands a nondogmatic style and a willingness to admit that not everything is known. Some students may feel chal- lenged to enter the field of sex research themselves in order to help fill those gaps in our understanding.
Some human sexuality texts contain a great deal of advice to students, especially in the area of relationships. Much of this advice has no objective basis and seems designed more to transmit the authors’ values than to foster an authentic learning experience. In Discovering Human Sexuality, we keep the total quantity of advice down and try to ensure that the advice we do give has been “field-tested.” Even in such an elementary matter as how to put on a condom, many texts include useless steps, such as squeezing the tip of the con- dom to leave space for the ejaculate. Doing so serves no pur- pose—the man who could burst a condom with his ejaculate has yet to be born—and neither the World Health Organiza- tion nor the leading U.S. experts believe that it should be part of the instructions for condom use. It has become an element in the folklore that gets perpetuated by textbooks— though not by this one.
Literature citations are, of course, an important element of an evidence-based book. We have been surprised by how cavalierly some competing books deal with this issue—quite commonly, citations in the text are not matched by any cor- responding entries in the bibliography. In Discovering Human Sexuality we have made every effort to ensure that references are fully documented. Another common practice that we consider unacademic is referring to original research stud- ies by citing magazine or newspaper articles that mention
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xxII PREFACE
them, rather than the journal articles in which the research was presented. Our policy has been to cite original sources wherever possible, and to use magazine and newspaper ref- erences for the kinds of topics they excel at, such as news stories, cultural trends, and the like.
emphasis on diversity Today’s college students come from a wide range of backgrounds, and in their adult lives they will have to deal with people very different from themselves. Our text presents this diversity in a detailed and nonjudgmental fashion. For example, with regard to sexual orientation, we go far beyond “gay,” “bisexual,” and “straight”: We talk about the ever-changing history of the butch-femme dichotomy in lesbian culture, women whose self-identity is too fluid for one-word labels, gay men who are “bears” or “bear cubs” or into the leather scene, what it’s like to be gay and Asian-American or Native American, how the gay experience differs for different generations of Americans and for gay people around the world, and so on. Similarly, we take pains to discuss racial, ethnic, and religious diversity, as they affect sexuality, and of course diversity in the actual modes of sexual behavior—includ- ing some of the more unusual forms of sexual expression such as “adult babies” and men whose partners are (liter- ally) dolls.
presentation style Simon LeVay, Janice Baldwin, and John Baldwin are all experienced authors of college text- books. In creating Discovering Human Sexuality, we have pooled our writing skills to ensure that the text is fully ac- cessible, engaging, and relevant to students of diverse back- grounds. The result of these combined efforts is, we believe, the most readable and student-friendly human sexuality text on the market.
art program Another way that we have striven to main- tain both comprehensibility and interest is through the illus- trations. One might think that it would be a simple matter to illustrate a book on human sexuality, but in reality it is a significant challenge. Illustrating some of the concepts dis- cussed in this book, especially in its more biologically orient- ed sections, requires a great deal of thought and design skill. Our publisher, Sinauer Associates, is an industry leader in the use of art as a pedagogical medium. Thanks to our pub- lisher’s efforts, many complex topics, such as the regulation of the menstrual cycle, have been given a visual representa- tion that gracefully parallels and clarifies the accompanying text. Nearly every two-page spread in the book offers one or more illustrations—photographs, drawings, diagrams, graphs, or charts—relevant to the text on that spread. Besides their informative value, illustrations offer important visual relief. Some of our competitors’ texts contain sequences of
up to ten pages without a single illustration—a definite chal- lenge to the average student’s attention span.
boxes The 76 boxes are an important feature of the book. The boxes are organized into eight themes: Controversies; Biology of Sex; Cultural Diversity; Research Highlights; Sexual Health; Sex in History; Personal Points of View; and Society, Values, and the Law. Within each theme, the sub- jects range from the serious to the lighthearted, but they all attempt to broaden the reader’s horizons with a more in- depth look at specific questions than is possible within the main text: What exactly does “losing one’s virginity” mean to today’s teenagers, behaviorally and emotionally? Is there more than one kind of female ejaculation? What’s it like to be a rubber fetishist? Why do some Amazonian peoples be- lieve that a child can have several fathers? In tackling these and many other questions, the boxes provide breaks from the steady flow of the text and allow students to consider specific issues in a more relaxed and informal way.
Other aids to learning and revision include key terms (indi- cated by boldfaced type and defined in a running glossary), FAQs (frequently asked questions), discussion questions, chapter summaries, Web resources, and recommended reading materials.
Discovering Human Sexuality’s student companion web- site (sites.sinauer.com/discoveringhumansexuality3e) is an invaluable learning aid. This site parallels the text with a thorough set of study questions, animations, activities, Web topics, quizzes, and other resources. Website activities are linked to the text and are referenced in maroon type in the printed text. In addition, a complete set of instructor supple- ments is available to qualified adopters of the textbook. See the section on Media and Supplements for details on the full range of material that accompanies Discovering Human Sexuality.
The Third Edition The following are examples of the many changes that we have made for the Third Edition: zz Chapter 1, “Sexuality: Pathways to Understanding,”
has been thoroughly rewritten. It now pays less attention to the history of sex research and more to the diversity of methods that are used to study sexu- ality. We discuss a specific example of the use of each methodological approach. zz We have added discussions of many topics that
were not covered, or only briefly covered, in earlier editions. These topics include group sex (Chapter 6); data-mining studies based on OkCupid and
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http://sites.sinauer.com/discoveringhumansexuality3e
other websites (Chapters 5, 12, and elsewhere); the influence of physical attractiveness on men’s and women’s satisfaction with their long-term relation- ships (Chapter 5); the new definitions of paraphilias and paraphilic disorders in DSM-5 and the contro- versy surrounding them (Chapter 13); the current debate on how to respond vigorously and yet fairly to allegations of campus rape (Chapter 16); and the personalities and attitudes of men who use prosti- tutes (Chapter 17). We have also deleted numerous passages that seemed less interesting or instructive than they were a few years ago. zz We have added 19 new boxes on a wide range of
topics, including “Foot Orgasms,” “Pain-free Child- birth,” “Feticide,” “Why Gay Genes?” “STIs and the Law,” and “What’s It Like to Be a Porn Star?” zz We have of course taken the opportunity to update
the book with the latest research, surveys, statistics, laws, medical advances, contraceptive techniques, and cultural happenings. zz The two appendices cover material that was not
included in Discovering Human Sexuality, Second Edition. We present this material in the form of appendices so that instructors may include it or not as suits the purposes of their classes and the interests and backgrounds of their students. Appendix A is an abbreviated and updated version of the chapter “Sex and Evolution” from Human Sexuality, Fourth Edi- tion. It tackles important questions that are addressed in few other undergraduate human sexuality text- books, such as: What is the adaptive value of sexual reproduction? How does sexual selection work? What are the benefits and costs of male and female promiscuity? and What is the basis of incest avoid- ance? Appendix B lays out more detail on the role of the nervous system in sexual behavior and physiol- ogy than is presented in the main text, including, for example, the anatomy and functional role of the autonomic nervous system in genital responses.
Acknowledgments Producing a modern college textbook such as this one requires the combined efforts of a much larger team of professionals than the three of us who are privileged to have our names on the front cover. The staff members of Sinauer Associates have produced, with great efficiency and good humor, a textbook of outstanding visual quality and educational value. Those with whom we have had the most enduring contacts are editor Sydney Carroll, produc- tion editor Martha Lorantos, and photo researcher David
McIntyre, but many others labored behind the scenes to ensure the book’s high quality and timely production. We are especially grateful for the production oversight of Janice Holabird and Christopher Small, and for the creative cover design by Joan Gemme. We also thank Lou Doucette for her skillful copyediting; Jason Dirks, Carolyn Mailler, Mara Sil- ver, Suzanne Carter, Ann Chiara, Thomas Friedmann, and Nate Nolet for their work on the media and supplements package; Marie Scavotto, Nancy Asai, and Susan McGlew for their effective work promoting the book; Johanna Walko- wicz for obtaining outside reviews; and Penny Grant for sending us our checks on time!
Reviewers We acknowledge with gratitude the extensive and construc- tive comments made by the people who reviewed chapters of Discovering Human Sexuality for the new edition. These reviewers are listed below. Helpful comments have also come from the Baldwins’ students at the University of Cali- fornia, Santa Barbara.
Ernest Abel, Wayne State University Amy Beeman, San Diego Mesa College Kimberly Blackwell, Hampton University Elizabeth Calamidas, Richard Stockton College Michael Clayton, Youngstown State University Karen Gee, Mission College Samantha Gibeau, Lane Community College John Hallock, Pima Community College Julie Harris, East Carolina University Lynda Hoggan, Mt. San Antonio College Nathan Iverson, California State Polytechnic University, Pomona Jason Lavender, North Dakota State University Janet Lever, California State University, Los Angeles Vicki Lucey, Modesto Junior College Stephanie Marin, California State Polytechnic University, Pomona Wanda C. McCarthy, University of Cincinnati Clermont College Heather Meggers, Birmingham Southern College Tami James Moore, University of Nebraska at Kearney Peggy Oberstaller, Lane Community College Carolyn Peterson, University of Cincinnati Jason Rothman, California State Polytechnic University, Pomona Justine Shuey, Montgomery County Community College Peter Sparks, Oregon State University–Cascades Paul Vasey, University of Lethbridge James Vaughn, University of Science and Arts of Oklahoma
PREFACE xxIII
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Media and Supplements to accompany Discovering Human Sexuality, Third Edition
For the Student Companion Website sites.sinauer.com/discoveringhumansexuality3e
The Discovering Human Sexuality, Third Edition Companion Website includes a robust set of study and review aids—all available at no cost to the student. This online companion to the textbook takes the place of a printed study guide and includes the following resources: zz Chapter Outlines: Complete outlines of each chapter
provide an overview of the chapter and include links to the relevant Study Questions for each section. zz Chapter Summaries: A thorough review of each chap-
ter’s content. zz Learning Objectives: The objectives help focus the
student on the important concepts and topics in each chapter; each is referenced to specific textbook head- ings and pages. zz Activities: For selected chapters, animations, dynamic
illustrations, and labeling exercises help the student learn and understand complex concepts and ana- tomical (and other) terms. zz Study Questions: An extensive set of interactive self-
study questions covers the full range of content in every chapter. zz Flashcards: Students can quiz themselves on all the
important terms from each chapter, or they can browse the list of terms as a review. zz Web Links: A set of online sites and resources relevant
to each chapter. zz Glossary: A complete online version of the book’s
glossary. zz Online Quizzes: Two sets of questions are available
for each chapter, for instructors to assign or make available to students as review exercises (instructor registration required): zz Multiple-Choice Quizzes test student compre-
hension of the material covered in each chapter. zz Essay Questions challenge students to synthe-
size and apply what they have learned.
For the Instructor (available to qualified adopters)
Instructor’s Resource Library The Discovering Human Sexuality, Third Edition Instructor’s Resource Library (IRL) contains a wealth of resources for use in course planning, lecture development, and assessment. Contents include: zz Textbook Figures & Tables: All of the textbook’s figures
(both line art and photographs) are provided as JPEG files at two sizes: high-resolution (excellent for use in PowerPoint) and low-resolution (ideal for web pages and other uses). All the artwork has been reformatted and optimized for exceptional image quality when projected in class. zz PowerPoint Resources: Two ready-to-use presentations
are provided for each chapter: zz A lecture presentation that includes text cover-
ing the entire chapter, with selected figures. zz A figures presentation that includes all the fig-
ures and tables from the chapter. zz Instructor’s Manual: The Instructor’s Manual pro-
vides instructors with a variety of resources to aid in planning their course and developing their lectures. For each chapter, the manual includes a chapter overview, a chapter outline, the complete chap- ter summary, class discussion questions, teaching resources, and suggested readings. zz Media Guide: The Media Guide includes extensive
lists of suggested video segments (and full-length titles) that are ideal for use as lecture starters or other in-class activities. Video suggestions (with links and sources) are provided for topics across all chap- ters, and suggested discussion questions are also included. zz Test Bank: The Test Bank consists of a broad range of
questions covering all the key facts and concepts in each chapter. Each chapter includes multiple-choice, fill-in-the-blank, and, new for the Third Edition, short answer questions. Also included are all of the Companion Website quizzes (multiple-choice and essay), the textbook end-of-chapter questions, and
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MEDIA AND SUPPLEMENTS xxV
the Media Guide discussion questions. All questions are keyed to Bloom’s Taxonomy and referenced to specific textbook sections. zz Computerized Test Bank: The entire test bank is pro-
vided in Blackboard’s Diploma software. Diploma makes it easy to assemble quizzes and exams from any combination of publisher-provided questions and instructor-created questions. In addition, quiz- zes and exams can be exported to many different course management systems, such as Blackboard and Moodle.
Online Quizzing The Discovering Human Sexuality Companion Website fea- tures pre-built chapter quizzes (see above) that report into an online gradebook. Adopting instructors have access to these quizzes and can choose to either assign them or let students use them for review. (Instructors must register in order for their students to be able to take the quizzes.) Instructors also have the ability to add their own questions and create their own quizzes.
Value Options eBOOK Discovering Human Sexuality, Third Edition is available as an eBook, in several different formats. The eBook can be pur- chased as either a 180-day rental or a permanent (non-expir- ing) subscription. All major mobile devices are supported. For details on the eBook platforms offered, please visit www. sinauer.com/ebooks.
Looseleaf Textbook (ISBN 978-1-60535-379-1) Discovering Human Sexuality is available in a three-hole punched, looseleaf format. Students can take just the sec- tions they need to class and can easily integrate instructor material with the text.
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http://www.sinauer.com/ebooks
http://www.sinauer.com/ebooks
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Discovering Human Sexuality
third edition
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1Chapter
Sexuality is a fundamental aspect of human nature.
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Sexuality: Pathways to Understanding
Sexuality is a central and all-pervasive theme of human existence. At its best, sexuality charges our lives with energy, excitement, and love. It offers a deep sense of connectedness, capable of spanning and healing social divisions. It creates family, the primary unit of society and the cradle of future generations.
At its worst, sexuality brings prejudice, anguish, violence, and disease. To begin our exploration of this powerful and mysterious force, we first
ask what the terms “sex” and “sexuality” mean and why sexuality is a topic worth studying. We go on to review some of the ways in which human sexuality has changed between the origin of our species and the present day. Our purpose is to make clear that, even though there may be some eternal truths about sexuality, it is not static: It changes slowly as a result of evolutionary forces, and much faster under the influence of culture. We then go on to describe the variety of methods by which sexuality can be studied, methods that will be applied repeatedly throughout the remainder of the book.
To do it justice, we must approach human sexuality with open minds, with respect for diversity, and with all the modes of inquiry that have been used to illuminate human nature. Approached in this way, the topic is not just another step in your college career: It is a personal voyage of discovery that will help you to enjoy the best that sexuality has to offer, and to avoid the worst.
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4 chapter 1
Sexuality Is a Broader Concept than Sex The term sex has two meanings. First, it means the distinction between female and male—a distinction that, as we’ll see in later chapters, is not as clear-cut as you might imagine. Second, it means engaging in sexual behaviors. These behaviors may be very obviously sexual because they are marked by genital phenomena such as vagi- nal lubrication, penile or clitoral erection, orgasm, and so on. But they also include behaviors that do not directly involve the genitals, such as courtship, as well as behaviors such as kissing that may or may not be sexual depending on context.
The term sexuality includes sex but also goes beyond it to encompass the entire realm of human experience that is more or less closely connected with sex. It means, for example, our gendered traits—the psychological traits that differ, to a greater or lesser extent, between women and men. It means our sexual and romantic attrac- tions and relationships—who we find attractive or fall in love with, and how we establish, maintain, or dissolve sexual partnerships. It means becoming a parent (or preventing that from happening). It also includes the two-way relationship between our personal sexual identities and behaviors and social structures such as the law, religion, medicine, and politics.
Studying Sexuality Has Practical Benefits There are many possible reasons why you have chosen to take a course in human sexuality. Maybe you’re simply curious about a topic that is often treated with embar- rassment, evasion, or flippancy. Maybe you are looking for ways to improve your own sex life, or you think you have sexual problems that need to be solved. Maybe you are planning a career that requires an understanding of human sexuality.
Regardless of your specific motives, many practical benefits are to be gained from taking this course and reading this textbook. Here are some examples:
zz Improving your understanding of the structure and function of your geni- tals and those of your partners will help you give and receive more plea- sure from sex. zz Learning more about how people communicate on sexual topics will
increase your chances of forming and maintaining satisfying relationships and avoiding abusive ones. zz Learning about sexual diversity will encourage you to be more under-
standing of unusual sexual desires and behaviors—whether in others or in yourself. zz Educating yourself about contraception and sexually transmitted infections
will lessen the chance that your sexual behavior may end up harming you or your partners. zz Becoming knowledgeable about sex will be an asset to you in your future
career—most especially if you enter the medical or helping fields, but also in any career that brings you into contact with other people. zz Educating yourself about sex will enable you to educate others—including
your friends and your own children, if you plan to have them. zz By learning to think critically about research, you will become a more
discriminating consumer of media reports and advertising relating to sexuality.
Sexuality Has Changed over Time Most—but not all—women and men experience sexual desire and engage in sexual relationships at some point in their lives. This has likely been true across the course of
sex A person’s identity as female or male, or sexual behavior.
sexuality The feelings, behaviors, and identities associated with sex.
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Sexuality: pathwayS to underStanding 5
human history and prehistory, and it is true around the world today. But the ways in which these desires and relationships express themselves have been extraordi- narily varied. Here we sketch some of the changes that have occurred over time.
Sexuality has been influenced by evolution Humans evolved from the common ancestors of humans and nonhuman pri- mates, who lived about 7 million years ago. You might think that we could get some idea of early human sexuality by studying the sexual behavior of our clos- est relatives, the great apes (chimpanzees, bonobos, gorillas, and orangutans), on the assumption that these animals have changed less over time than we have.
It turns out, however, that there is a great deal of sexual diversity even among these closely related species. Among chimpanzees, for example, most sexual behavior is between males and females and has the potential to lead to preg- nancy. Among bonobos, which look very similar to chimpanzees, sexual contact between individuals of the same sex is common. The function of such behavior is clearly not reproductive; rather, it serves the purposes of conflict resolution and alliance formation (Parish & de Waal, 2000). Among orangutans coercive sex—analogous to rape in humans—is common (Knott et al., 2010), but that’s not true for bonobos. Some of these species differences are described in Appendix A.
One general characteristic of sexual behavior among our primate relatives is that more of it takes place than is strictly necessary for reproductive purposes—some- times a great deal more. Another is that individuals compete for sex partners: Males often compete for access to the most fertile females, while females often compete for the attention of high-ranking males. You don’t have to be a sex researcher to know that these kinds of competition are prevalent in our own species today. It’s likely that competition for partners has characterized sexuality throughout human history and prehistory, and that this competition has driven the evolution of sex differences in appearance and behavior.
Early in the evolution of our species, humans probably lacked understanding of the connection between coitus (penile-vaginal intercourse) and reproduction. Of course, they acted as if they understood, just as our primate relatives do, but their sexual behavior was actually driven by instincts that required little conscious aware- ness. Even today, there are human cultures where people are unaware of biological facts that seem obvious to us, such as the fact that a child has just one father, or that pregnancy and childbirth result from a single act of coitus (Box 1.1).
Over the course of human history the trend toward an increasingly conscious understanding of how sex “works” has influenced human sexuality in directions that seem counterintuitive in evolutionary terms. For example, the knowledge that the deposition of semen (the male ejaculate) in the vagina is what causes pregnancy led to the introduction of contraceptive practices. These included withdrawal of the penis prior to ejaculation—a practice known already in Old Testament times—and the use of various kinds of barriers placed in the vagina. Similarly, methods intended to interrupt an established pregnancy—by use of certain herbs or poisons, or by black magic—were widely used in the Middle Ages, with varying success. As methods for contraception and abortion have improved over the centuries, so has it become increasingly possible to enjoy the pleasures of sex without its natural consequences. This has undoubtedly increased people’s—especially women’s—willingness to engage in sex both within and outside of established relationships.
Society has changed sexuality Human sexuality has been greatly influenced by the development of social controls. The transition from a hunter-gatherer lifestyle to one of settled agriculture took place coitus Penile-vaginal intercourse.
Male primates, such as these golden snub-nosed monkeys, often fight over access to females.
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in the Middle East roughly 10,000 years ago. This transition led eventually to the formation of city-states, which required governments and the regulation of social behavior. Nudity was restricted, in part with the aim of reducing sexual arousal, pre- venting the sight of sexual arousal in others, and eliminating sexual conflicts. (Some present-day hunter-gatherer cultures still permit nudity.) Marriage was formalized, and nonmarital sex was discouraged to a greater or lesser degree.
Meet My Dads no matter how many men a woman has sex with, any child she bears has only a single biological father—the man whose sperm fertilized the woman’s ovum. in most cultures around the world, people accept this reality of single paternity. yet anthropologists have discovered an exception among many of the indigenous tribal societies of lowland South america (amazonia and nearby areas). here people believe that a man’s semen remains in the woman’s body indefinitely after sexual intercourse, so if several different men have sex with her before she becomes pregnant, then all of them contribute to the making of her child (Becker- man & Valentine, 2002).
this belief is called partible paternity (“divisible fatherhood”). By studying language relationships among the societies where partible paternity is found, anthropologist robert walker of the university of Missouri and his colleagues have traced it back to the distant past, probably to the time when the lowlands were first settled and the settlers spoke a common language (walker et al., 2010).
what benefit does the concept of partible paternity confer? anthropologists such as william crocker of the Smithsonian institution have found that the societies that believe in parti- ble paternity engage in distinctive sexual practices (crocker & crocker, 2003). they may participate in rituals in which women engage in sex sequentially with multiple men. and unlike in other cultures, where men typically guard their wives from sexual con- tact with other males, men in these amazonian tribes may freely offer their wives to male relatives as well as to powerful men who are actual or potential allies.
partible paternity, and the practices associated with them, benefit women’s efforts to raise children. that’s because the multiple “fathers” of a given child may give gifts in exchange for sex, may support or protect the child, or may at least refrain from killing the child. (the killing of infants and children by men has traditionally been a significant cause of mortality in ama- zonian cultures.)
what about the men? on the face of it, the notion of par- tible paternity seems to disadvantage them, because they may
end up supporting children who are not biologically theirs. on the other hand, they are “hedging their reproductive bets” by spreading their semen widely. this may be of particular value to high-status men, who gain disproportionate access to other men’s wives, thanks to partible paternity. in addition, partible paternity gives men some assurance that their biological chil- dren will have male support in the event of their own premature death, something that’s all too common in amazonia.
this still leaves unanswered the question of why partible paternity is common in lowland South america but rare else- where. the answer may be related to the importance of kin- ship and alliances in those societies, combined with a general absence of material wealth. in such circumstances paternity may be used as a unit of wealth that can be traded, as it were, in social networks.
partible paternity the belief that two or more men may be fathers of the same child.
This Araweté woman of Brazil may believe that two or more men fathered her son.
Box 1.1 Cultural Diversity
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Organized religion played a role in these changes (Endsjo, 2011). Although religious teachings have varied greatly, they have often fostered procreative heterosexual sex within marriage while labeling other forms of sexual expression as sinful. This was particularly true for the Christian religion: For most of the two millennia since its foundation, Christian teachings forbade all nonmarital sex, homo- sexual sex, masturbation, contraception, abortion, and polygamy. Even marital sex was restricted to coitus in certain positions, and it was forbidden on certain days of the week and during Lent (Ranke-Heinemann, 1990). Priests were commonly barred from marriage or any kind of sexual activity. This changed to some extent after the Reforma- tion, when western Christianity splintered into numerous denominations, some of which have become much more liberal in the area of sexual ethics compared with the Catholic Church.
The development of large-scale societ- ies led to the emergence of class structures, with the rich and powerful at the top and the impoverished masses at the bottom. What class you belonged to greatly influenced your sex life. Take India: The Kama Sutra, compiled around the 2nd century, describes innumerable ways for men to obtain sexual pleasure and to give sexual pleasure to women (Vatsyayana, 1991) (Figure 1.1). It also describes sex between women and between men. But the Kama Sutra was written for and about the idle rich. (What to do between breakfast and lunch? Teach your parrot to talk.) If the sex lives of low- caste Indians were anything like they are today, they involved hasty, fully-clothed couplings with the minimum of pleasure or romance (Nath & Nayar, 1997).
Another way that class influenced sexuality had to do with polygamy. The major- ity of human cultures have permitted men to have more than one wife, but it was largely rich and powerful men who did so, because they had sufficient means—King Solomon is said to have had a thousand wives. Polygamy reduced the numbers of available women and thus made it harder for poor men to afford even one wife. What’s more, polygamy is connected with the idea that women are men’s property— if a rich man has many cattle, why shouldn’t he have many wives? By banning polyg- amy, the Christian religion promoted a somewhat more gender-equitable society.*
Across history, large numbers of men have been deprived of a sex life altogether by being castrated—that is, by having their testicles removed, and sometimes the penis also. Such men were called eunuchs. Castration was carried out as a punish- ment among criminals or prisoners of war, or (if done before puberty) to produce asexual male slaves who could serve certain roles such as court attendants, harem guards, dancers, or singers. Some eunuchs achieved powerful positions in imperial courts across Asia. In India, some men were (and still are) voluntarily castrated as an initiation into the transgender religious caste known as hijras, who are described further in Chapter 4 (Nanda, 1998).
Figure 1.1 The Kama Sutra describes a wide variety of sexual positions.
* In early Islam, polygamy helped provide for the many women whose husbands died in warfare.
heterosexuality Sexual attraction to, or behavior with, persons of the opposite sex.
homosexuality Sexual attraction to, or behavior with, persons of the same sex.
polygamy Having more than one spouse at the same time, as a social institution.
castration Removal of the testicles or testicles and penis.
eunuch A man who has been castrated.
transgender (or trans) Identifying with the other sex or rejecting gender norms.
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In general, castration has served the interests of noncastrated men, especially powerful men, and it therefore represents another way in which class and sexuality interact. Today, castration by surgery or “chemical castration” by drugs is performed voluntarily on some men with prostate cancer in an effort to prolong their lives—per- haps a quarter of a million American men are in this situation (Wassersug et al., 2014).
Another important effect of cultural change has involved sexually transmitted infections. When people lived in small groups and stayed in a restricted area, they tended to reach a biological accommodation with the infectious agents (bacteria and viruses) present in that population, such that their effects were not especially severe. Increases in population density and long-distance travel changed this picture: The organism that causes syphilis, for example, was present in the native populations of the Americas long before the arrival of Columbus and other explorers, but when these men returned to Europe, bringing the organism with them, it unleashed a dev- astating epidemic (Rothschild et al., 2000). Potentially fatal diseases such as syphilis and (more recently) AIDS made sex itself seem frightening and sinful.
Marriage has been transformed Yet another important change has been the radical decline in birth rates that has taken place in most countries, starting in the late 18th century. Over this period the number of children born to the average American woman has fallen from 7 or 8 to about 2 (Figure 1.2). Today, there are plenty of women or couples who choose to have no children at all—something that used to be quite unusual, except for women in religious orders. This decline has not been accompanied by any decline in people’s interest in sex. Thus the idea has gained currency that sex has a legitimate emotional or recreational function, beyond the production of children.
The institution of marriage has changed over time (Abbott, 2011). In many tradi- tional societies marriage signified the transfer of ownership of a woman from her father to her husband; marriages were negotiated and often involved large bridal payments. People fell in love, but they were lucky if they married the people they fell in love with. In Europe and America, even as late as the 19th century, a suitor was expected to ask the girl’s father for permission to propose to her, and if permis- sion was refused—because the young man had insufficient means, for example—the young couple’s only recourse might be to run away (elope) and marry at some distant location.
A woman was expected to be a virgin when she married, but a man could be forgiven or even admired for “sowing his wild oats.” (This was an example of the double standard, by which males and females were, and still may be, held to differ- ent moral codes.) The husband’s and wife’s roles in marriage were also quite distinct:
double standard The idea that acceptable behavior is different for men than for women.
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Figure 1.2 Declining birthrates This graph shows the average number of children born to American women between 1800 and 2010. The data for white and African-American women are plotted separately.
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The husband was the breadwinner, the wife the homemaker and child rearer, perhaps with the help of servants.
Before the 20th century, marriage was for life: Divorce was quite uncommon and was only permitted in cases of proven adultery. Divorce laws were greatly liberalized over the course of the 20th century, and now nearly half of all U.S. marriages end in divorce rather than death (Wilcox & Marquardt, 2011). What’s more, it’s now widely accepted that women are sexually active before mar- riage, and that couples may live together (cohabit) before mar- riage or without marrying at all. And the birth of children outside of marriage, once a shocking secret, is now more or less routine: Over 40% of all U.S. births are now to unmarried women, who may be single or cohabiting with a man or with a woman (Martin et al., 2013).
Up until the mid-20th century the vast majority of Americans considered inter- racial marriage to be sinful, and such marriages were illegal in many states. Atti- tudes changed gradually after World War II, and in 1967 the U.S. Supreme Court established a constitutional right to marry across racial lines (Figure 1.3). Currently we are witnessing a similar trend with regard to same-sex marriage, but gay couples who marry today are joining an institution that has lost a great deal of its former significance.
Sex has become a topic of social discourse The 20th century saw a dramatic increase in people’s willingness to talk about sex. At the beginning of the century Victorian prudery still ruled: Most people could talk about sex only obliquely, if at all. Then came a series of outspoken researchers and activists whose work turned sex into a hot topic of conversation. Here are a few of them:
zz Havelock Ellis (1859–1939) was an English physician who described unusual kinds of sexual expression (which had previously been called “perversions”) in a sympathetic rather than a condemnatory way. zz Sigmund Freud (1856–1939) was an Austrian neurologist and founder
of psychoanalysis. He proposed that our lives are governed by a roiling unconscious world of sexual drives and conflicts (Box 1.2). zz Margaret Sanger (1879–1966), an American social activist, campaigned
tirelessly and effectively for women’s right to learn about and practice contraception. zz Alfred Kinsey (1894–1956) was an Indiana University biologist whose pio-
neering sex surveys (the “Kinsey Reports”) caused a sensation when they were published in 1948 and 1953 (Figure 1.4). zz Margaret Mead (1901–1978) was an American cultural anthropologist who
described the sexually uninhibited lifestyles of some Pacific Islanders. zz William Masters (1915–2001) and Virginia Johnson (1925–2013), of Wash-
ington University in St. Louis, pioneered the physiological study of sexual responses in healthy people and in those with sexual disorders.
cohabitation A live-in sexual relationship between individuals who are not married to each other.
Figure 1.3 Supreme Court justice Clarence Thomas and his wife Virginia are one of the many couples who have benefited from the court’s 1967 ruling that there is a constitutional right to marry across racial lines.
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School sex education, which is now mandated in 22 U.S. states (National Conference of State Legislatures, 2014) and throughout Canada, has also promoted discussion and awareness of sexual issues. Even today, though, many Americans find it difficult or inappropriate to talk about sex, and in some more-conservative cultures it may be completely off-limits.
Social movements have affected sexuality Political and social movements have impacted sexuality in America and elsewhere. In the 1970s and 1980s the women’s movement asserted women’s right to control their own bodies (through contraception and abortion, for example), to be free of sexual coercion, and to seek pleasure in sexual relationships. The idea gained ground that men shared responsibility for ensuring that their female partners experienced pleasure, including orgasm, during sex.
The gay liberation movement led to the increasing acceptance of homosexuality, which led in turn to the enactment of anti-discrimination laws, starting in the 1980s, and the nationwide legalization of gay sex by a 2003 ruling of the U.S. Supreme Court. Advocates have campaigned for recognition and social acceptance of many other facets of sexuality: bisexuality, asexuality, transgender identity, intersexual- ity, plural marriage (polygamy), polyamory, sadomasochism, fetishes, pedophilia, pornography, and prostitution. (If some of these terms are unfamiliar to you, don’t worry: We will be covering them all in later chapters.) Although these efforts have met with widely varying success—and rightly so, you may think—what they have done is change the conversation: Sexual expression, it’s now increasingly agreed, should be legally restricted only when it makes rational sense to do so, not simply when it runs afoul of tradition, prejudice, or good taste.
Of course, sexuality doesn’t just change over time; it also varies widely from place to place around the present-day world, and among individuals within the same population. We will focus primarily on North America, the region where this text is used, but from time to time we will make trips overseas to look at examples of global diversity in sexual behavior and ideas about sexuality.
Figure 1.4 Let’s talk about sex. Sex researcher Alfred Kinsey (far right) lectures at the University of California in 1949.
What was the “sexual revolution” of the 1960s?
It was a youth-led movement for greater sexual freedom and indi- viduality, driven by rebellion against the more orthodox World War II generation and fueled by feminism, the contraceptive pill, rock and roll, and drugs. An enduring conse- quence was the greater acceptance of sex outside of marriage.
FAQ
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Freud and Hirschfeld: Contrasting Theories on Sexual Orientation about a century ago, two european doctors proposed radically different theories to account for why some people are sexually attracted predominantly to members of the other sex while oth- ers are attracted to members of the same sex or to both sexes— a characteristic we now call sexual orientation. in Vienna, Sig- mund Freud (Figure A) developed a theory that was based on the concept of an unconscious mind, whose operations could supposedly be probed by psychoanalytic techniques such as free association, the interpretation of dreams, and slips of the tongue. the unconscious mind, though hidden from view and free from moral restraints, nevertheless resembled the con- scious mind in many respects—both were capable of rational thought, planning, memory, and emotion.
in Freud’s conception, the unconscious mind was more broadly focused in its sexual desires than was the conscious mind. this was particularly true during early childhood, which he believed included autoerotic and homosexual phases as well as incestuous desires directed toward one or the other parent. Freud thought that the “normal” progression to adult hetero- sexuality could be derailed in various ways, often involving unconscious emotional processes such as a hostile, too-close, or jealous relationship with a parent or sibling. these phenom- ena could lead to what Freud called perversions, that is, men- tal states in which adult sexual desires were directed toward atypical targets, such as people of the same sex (homosexu- ality), inanimate objects (fetishism), and so on. or they could lead to neuroses, in which the sexual element was supposedly repressed from consciousness altogether and reemerged in the form of nonsexual traits and disorders, such as obsessive- compulsive behaviors, depression, or “hysteria.”
in Berlin, Magnus hirschfeld (Figure B) took a quite different view. hirschfeld proposed the existence of two neural centers in the brain that were responsible for sexual attraction to men and to women, respectively. he suggested that during early fetal life all humans possessed both centers, but later one center grew and dominated, while the other regressed. in men, of course, it was usually the center for attraction to women that persisted, while in women it was the center for attraction to men. only in the minority of homosexual individuals did development take the opposite course. hirschfeld believed that sex hormones (then understood in only a very rudimentary way) channeled develop- ment in one direction or another, and that people also had a genetic predisposition to same-sex or opposite-sex attraction.
in many ways, the views of Freud and hirschfeld represented opposite approaches to understanding the mind and sexual- ity. Freud tried to understand the mind in terms of processes that, though hidden, were inherently mental—unconscious thoughts. and he believed interpersonal relationships held the key to sexual orientation and other aspects of adult sexuality.
to Freud, getting to your adult sexuality was a long, sometimes chaotic drama in which the unconscious mind took the leading role. hirschfeld, on the other hand, tried to reduce the mind to relatively simple nonmental phenomena such as the growth and activity of nerve cells, hormone secretion, and information encoded in the genes. in hirschfeld’s view, these phenomena controlled sexual development in a manner that was largely independent of family relationships and other aspects of life experience. to hirschfeld, getting to your adult sexuality was a process that unfolded mechanistically without your active par- ticipation—it simply happened to you.
Freud’s theories came to dominate most people’s ideas about the mind and sexuality through the early and middle part of the 20th century, while hirschfeld’s theories languished in obscurity. toward the end of the century, however, a noticeable shift of views occurred. to some people, Freud’s theories began to seem capricious, poorly substantiated, or inspired by prejudice (against women especially). Meanwhile, scientific advances tended to bol- ster a biological view of sexuality. Studies in animals showed that prenatal hormone levels do indeed influence sexual behavior in adulthood, and family studies supported the idea that genes do have some influence on sexual orientation in humans.
probably the dominant view at present is that both approaches offer potential insights into human sexuality. there must be some biological underpinnings to our thoughts and behaviors, and exploring these underpinnings is likely to tell us a lot about why people differ from one another sexually. on the other hand, it seems likely that some aspects of human sexuality need to be studied at the level of thoughts—in other words, by a cognitive approach. thus, even if neither Freud’s nor hirschfeld’s theories turn out to be entirely correct, they may both have contributed useful styles of thinking to the discussion.
perversion an obsolete term for atypical sexual desire or behavior, viewed as a mental disorder.
neuroses Mental disorders such as depression that, in Freudian theory, are strategies for coping with repressed sexual conflicts.
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Box 1.2 Controversies
(A) Sigmund Freud (B) Magnus Hirschfeld (1856–1939) (1868–1935)
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Sexuality Can Be Studied with a Wide Variety of Methods Investigators trained in many different disciplines make contributions to our under- standing of human sexuality. We could fill a whole book with an account of the meth- ods that are being used to study the topic. Here, we pick out some of the key areas and highlight certain research studies that illustrate the methods that are available.
Biomedical research focuses on the underlying mechanisms of sex Biomedical research is the approach that has the greatest practical impact on people’s sex lives. Here are a few examples:
zz Hormone-based contraception and abortion zz Drug treatments for reproductive cancers zz Drug treatments for erectile disorder, premature ejaculation, and low male
sex drive (with research into drug treatments for female sexual disorders being, so far, less successful) zz Methods to prevent, cure, or effectively treat sexually transmitted infec-
tions, including AIDS zz Technologies to treat infertility in women and men zz Improvements in the safety of pregnancy and childbirth
Biomedical researchers often turn to nonhuman animals to deepen their understand- ing of human nature, including human sexuality. Animal research involves studying the structure, function, and development of bodily systems that are involved in sex and reproduction. Most of the advances listed above were made possible by research using laboratory animals. In addition, researchers study the sexual behavior of ani- mals, both in the laboratory and in the wild. Although this book is titled Discover- ing Human Sexuality, we make no apology for including a great deal of information about, or derived from, nonhuman species.
Still, the introduction of modern imaging technologies has enabled the direct study in humans of topics that earlier could only be studied in animals. This is particularly true for brain function, which can now be studied with a variety of imaging tech- niques (Figure 1.5). In addition, the decipherment of the human genome is enabling all kinds of advances, such as the ability to ascertain the sex of a fetus and to diagnose certain fetal abnormalities on the basis of a simple blood sample drawn from the mother. And as we’ll discuss in Chapter 12, current research is attempting to home in on genes that influence such important traits as a person’s sexual orientation.
One study that exemplifies the biomedical approach to sexuality was conducted by one of this textbook’s authors (Simon LeVay) about 25 years ago (LeVay, 1991). Basing his research on earlier work on laboratory animals, LeVay hypothesized that there might be structural differences between the brains of gay (homosexual) and straight (heterosexual) people. By examining the brains of deceased individuals, he found that a part of the brain involved in sexual behavior (a small region within a part of the brain known as the hypothalamus) was larger in straight men than in gay men. Other researchers extended this line of work to living people by the use of imaging techniques, and it’s now known that there are several differences in brain organization, not only between gay and straight men, but also between lesbian and straight women, as we’ll discuss in Chapter 12. Collectively, these studies helped shift our conception of homosexuality (and heterosexuality) from something that is learned or culturally imposed to something more akin to an inborn trait.
sexual orientation The direction of an individual’s sexual feelings: sexual attraction toward persons of the opposite sex (heterosexual), the same sex (homosexual), or both sexes (bisexual).
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Psychology includes diverse approaches to sexuality Psychology, the study of mental processes and behavior, has splintered into numer- ous overlapping subdisciplines, each of which tends to use distinct methods. The branch of psychology most significant to the study of sexuality is social psychol- ogy—the study of how we think about, influence, and relate to other people. Social psychologists concern themselves with all kinds of sexual matters, such as sexual attraction and relationships, violence between intimate partners, and anti-gay prejudice.
Here’s one example of how social psychologists tackle an important question relat- ing to sexuality. Researchers at UCLA, led by Neil Malamuth, have been interested in the question of whether portrayals of sexual violence in the media and pornog- raphy make men more accepting of such violence, as has been asserted by many feminists. Out of a group of male college students, half were randomly assigned to watch movies that portrayed sexual violence against women—specifically, movies in which a woman was raped but subsequently fell in love with her rapist. The other students (the control group) watched movies that contained no sexual violence. A few days later the students were given a sexual attitudes questionnaire. The results supported the feminist contention: Male students who watched sexually violent mov- ies expressed significantly more accepting attitudes toward sexual violence than the men in the control group. This and other studies have convinced the UCLA research- ers that exposure to images of sexual violence really does predispose some men to commit sexual assaults against women (Malamuth et al., 2000; Hald et al., 2010).
psychology The study of mental processes and behavior.
social psychology The study of one’s relationship to others.
feminism The movement to secure equality for women; the study of social and psychological issues from women’s perspectives.
control group A group of subjects included in a study for comparison purposes.
Figure 1.5 Sex on the brain This shows (in red) the average pattern of activity in the brains of ten women while they were experiencing orgasm, using a technique called functional mag- netic resonance imaging (fMRI). Activity immediately prior to orgasm has been digitally sub- tracted from the image, so the image shows activity related specifically to orgasm and not to general sexual arousal. Several parts of the brain are active during orgasm, but two areas of particular interest are the amygdala and hypothalamus, both of which play important roles in the regulation of sexual feelings and behaviors. (Image courtesy of Nan Wise and Barry Komis- aruk, Rutgers University.)
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Cognitive psychology is the study of internal mental processes. As an example, there’s a well-known stereotype that gay men are “like women” and lesbians are “like men.” How true is this? To find out, cognitive psychologists have conducted many studies comparing a variety of mental traits, skills, and attitudes in gay and straight people. Researchers at the University of Haifa, in Israel, for instance, picked empathy, which is the ability to detect and feel the emotions of other people. This trait is typically better developed in women than in men. Consistent with the stereotype, the researchers found that gay men scored higher on tests of empathy than straight men, whereas lesbians scored lower than straight women (Perry et al., 2013). Still, looking at the entire body of research in this field, gay people show a patchwork of gender-typical and gender-atypical traits, and what’s true on average is not necessar- ily true about individuals (LeVay, 2011). We review this topic further in Chapter 12.
Evolutionary psychology seeks to explain how evolution has molded our genetic endowment to favor certain patterns of sexual feelings and behaviors. One idea in evolutionary psychology is that because reproduction is so much more demanding for females than for males, genes have evolved that cause females to be very picky in their choice of sex partners. As a result, other genes have evolved that cause males to engage in competitive and risky sexual displays—displays that are intended to influence females’ choices.
It’s well established that men are more likely than women to engage in risky behaviors, but it’s not clear whether the risks we take in everyday life—such as when we cross a busy street—are actually sexual displays. To help answer this question, an international group of evolutionary psychologists descended on Britain’s University of Liverpool (Pawlowski et al., 2008). They stationed themselves near the campus’s busiest crosswalk, and over a period of 3 months they observed how 1000 men and women crossed the street (Figure 1.6). Specifically, they noted how much risk the stu- dents took in crossing (i.e., whether they crossed when vehicles were approaching) and who else was present when each person crossed. As might have been expected, the researchers found that men took more risks than women. The interesting finding, though, was that the presence of women nearby significantly increased the likelihood
that a man would attempt a risky crossing, whereas the presence of men nearby did not influence his decision one way or another. Women, on the other hand, paid little or no attention to who was present, regardless of their sex, when they decided whether to cross. The researchers concluded that even a mundane act such as crossing a street can be motivated in part by the urge to engage in sexual displays—but only for men in the presence of women. Women do engage in sexual dis- plays—when they flirt, for example—but these displays don’t commonly take the form of risk-taking behavior.
Another area of psychology is concerned with ethnic and cultural diversity in sexual attitudes, behavior, and relationships. This kind of research, which is conducted primarily by cultural anthropologists, involves field- work of the kind pioneered by Margaret Mead and oth- ers. An example is the research into the concept of parti- ble paternity in Amazonia that was discussed in Box 1.1. Another example closer to home concerns the Native American tradition of “two-spirit” people—individuals who incorporate both a male and a female identity and who are accorded a special role in their communities. These people have been studied in detail by anthropolo-
Figure 1.6 Looking for love? Crossing the street in front of traffic can be a form of sexual display, according to research at the University of Liverpool.
cognitive psychology The study of the information-processing systems of the mind.
evolutionary psychology The study of the influence of evolution on mental processes or behavior.
cultural anthropology The study of cultural variations across the human race.
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gist Walter Williams, who spent a great deal of time living among Native Americans (Williams, 1986). The study of two-spirit people challenges assumptions about gen- der that are prevalent in most Western societies (Sheppard & Mayo, 2013).
Sociologists focus on the connection between sex and society Sociology is the scientific study of society. Sociologists make a unique contribution to the study of human sexuality by linking the sexual behaviors and attitudes of indi- viduals to larger social structures. Sociologists examine how sexual expression varies with age, race, national origin, religious and political beliefs, place of residence, edu- cational level, and so on. Such studies are often carried out by means of sex surveys.
We already briefly mentioned the surveys conducted by Alfred Kinsey in the mid- 20th century. With the onset of the AIDS epidemic around 1980, the need for detailed information about sexual practices and attitudes spurred a host of new sex surveys. Most notable among the surveys was one conducted by sociologists at the University of Chicago and elsewhere—the National Health and Social Life Survey (NHSLS) (Laumann et al., 1994). A comparable British survey—the National Survey of Sexual Attitudes and Lifestyles (NSSAL)—was published in the same year (Wellings et al., 1994) and has been repeated twice, most recently in 2013 (Mercer et al., 2013). Besides being more up-to-date than the Kinsey surveys, the NHSLS and NSSAL were technically superior in a number of respects, especially in their use of modern random-sampling methods and advanced techniques of statistical analysis, made possible by computers.
One interesting finding of the NHSLS concerned masturbation. This practice is often thought of as something a person does as a substitute for “real” sex when part- ners are unavailable. No doubt this is sometimes the case, but the survey findings indicate that people usually masturbate in addition to engaging in partnered sex, not as a substitute for it. In fact, women with partners masturbate more than women without them, according to the survey.
In 2010, researchers at the Center for Sexual Health Promotion at Indiana Univer- sity published findings from a new National Survey of Sexual Health and Behav- ior (NSSHB) (Reece et al., 2010b). This survey obtained responses from nearly 6000 Americans age 14 to 94. Among the findings was a gender gap in the experience of heterosexual sex: More men than women experienced orgasm during their most recent act of penile-vaginal intercourse, whereas more women than men experienced pain.
Another valuable source of information is the General Social Survey (GSS), which is run by sociologists at the University of Chicago. The GSS has been asking Americans pretty much the same questions at 1- or 2-year intervals since 1972. Using the GSS survey data it is possible to find out how people’s attitudes toward, say, sex between unmarried couples, has changed over time.
From time to time throughout this book, we cite findings from these and other surveys. We also occasionally refer to magazine-sponsored surveys, which tend to cover intimate topics that the official surveys ignore. In 2012, for example, Esquire magazine commissioned a national random-sample survey that came up with all kinds of interesting information about current U.S. sex practices—such as that het- erosexual men’s favorite sexual position is the “cowgirl” (the woman straddling the man and facing forward) (Esquire, 2012).
Sex surveys are plagued with a variety of problems. It is often difficult to obtain truly representative samples of respondents. In addition, respondents may be reluctant to divulge details of their sex lives, especially if the information could be regarded as shameful. Kinsey tried to overcome this problem by the use of leading questions (“When did you first . . . ?” rather than “Have you ever . . . ?”). In more recent surveys researchers have attempted to reduce the embarrassment factor by
gender The collection of psychological traits that differ between males and females.
sociology The scientific study of society.
National Health and Social Life Survey (NHSLS) A national survey of sexual behavior, relationships, and attitudes in the United States, conducted in the early 1990s.
National Survey of Sexual Attitudes and Lifestyles (NSSAL) A periodic British survey of sexual behavior, relationships, and attitudes, most recently conducted in 2013.
National Survey of Sexual Health and Behavior (NSSHB) A national survey of sexual behavior in the United States, based at Indiana University and published in 2010.
General Social Survey (GSS) A long-running periodic survey of the U.S. population run by the National Opinion Research Center.
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allowing interviewees to type their responses directly into a computer.
Random-sample surveys, even very large ones, are likely to encompass very few if any individuals who belong to “minorities within minorities,” such as Asian-American lesbians. Yet it is often these neglected groups about whom information is most needed. What’s more, when only a small percentage of the subjects belong to a certain group, their truthful responses may be swamped by frivolous responses from others. This apparently happened with a survey of U.S. adolescents called the National Longitudinal Study of Ado- lescent Health, or AddHealth: In this survey an improbably large number of students described themselves as gay, and they sometimes added other unlikely facts such as having artificial limbs or numerous children. The deception came to light in a repeat survey carried out on the same individuals when they were adults: By then the artificial limbs, the chil- dren, and the homosexuality had largely vanished (Savin- Williams & Joyner, 2013).
Sociologists are also interested in the mechanisms by which social structures (rang- ing from the family to the mass media) mold individual feelings and behaviors. One influential idea is that society gives us “scripts”—ways of presenting ourselves to others as we deal with social interactions. We can select from many different scripts and ad-lib on them too. This idea has been referred to as script theory (Reiss, 1986; Simon & Gagnon, 1986; Frith, 2009).
Here’s an example of the application of script theory to a sexual topic: Angela Bartoli and Diane Clark of Shippensburg University studied the dating scripts typi- cally used by college students. They found that men’s scripts were far more likely to involve an expectation of sex, whereas women’s scripts typically included a respon- sibility for setting limits on sexual interactions (Bartoli & Clark, 2006). This is, of course, consistent with traditional views about men’s and women’s roles in sexual negotiations. Bartoli and Clark’s finding suggest that several decades of “women’s lib” did not change this dynamic in any significant way.
Sociologists may also engage in ethnographic fieldwork, immersing themselves in their subjects’ lives in the same way that cultural anthropologists do. For exam- ple, Staci Newmahr, then a graduate student in sociology at the State University of New York (SUNY) at Buffalo, wanted to explore the lives and motivations of people who engaged in BDSM activities (Newmahr, 2011). (“BDSM” means the infliction or receipt of pain, humiliation, and the like as a sexual or recreational outlet.) To do so, Newmahr joined a BDSM club and submitted to treatments that you might consider extreme, or at least well beyond the usual requirements for a PhD. We report on some of her findings in Chapter 13.
The economic approach weighs costs and benefits How much is sex “worth?” Sometimes, as in the case of prostitution, the answer to this question can be expressed in dollar terms. But even when money doesn’t change hands, people calculate—consciously or unconsciously—the costs and benefits of sexual encounters and sexual relationships (Baumeister & Vohs, 2004). The cost may be counted not in money but in time lost from studies or career, or in the effect of a damaged reputation that lowers a person’s future value in the sexual marketplace. The benefit may not be sexual pleasure, but a secure relationship. Researchers will- ing to take a hard-nosed economic approach to these issues help us understand how much more there is to human sexuality than simple romance or “the joy of sex.”
script theory The analysis of sexual and other behaviors as the enactment of socially instilled roles.
ethnography The study of a cultural group, often by means of extended individual fieldwork.
Participants in sex surveys give more honest responses when they can do so without the presence of investigators.
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Sexuality: pathwayS to underStanding 17
As an example of this approach, let’s take a look at a study that focused on how the sex ratio (the ratio of males to females in a given population) influences sexual negotiations. A basic tenet of economic theory is that the value of scarce resources tends to rise, so if one sex is in a minority, mem- bers of that sex gain leverage in the heterosexual marketplace. Because males are typically more interested in uncommitted sex than are women, it might be expected that casual sex would be more common in popula- tions with an excess of females and less common where males are in the majority. Psychologist Nigel Barber tested this prediction by obtaining data on sex ratios and teen birthrates (a proxy indicator of uncommitted sex) in 185 countries (Barber, 2000). Sure enough, teen births were highest in countries with an excess of females, and the association was not a weak one: Nearly 40% of the variability in teen birthrates between countries could be explained by their sex ratios. In later chapters we’ll see how sex ratios impact the sex lives of Americans.
It’s worth emphasizing that individual researchers often cross the boundaries between the various disciplines just described, or collaborate with researchers from other backgrounds. Psychologists and neurosci- entists often work together, for example. This kind of boundary cross- ing has greatly enhanced researchers’ ability to understand the roots of sexual behavior and sexual diversity.
As we have seen, women and men in a variety of academic disciplines and walks of life have made important contributions to our understand- ing of human sexuality. Increasingly, however, there is a perception that sex research, or sexology, is an academic discipline in its own right. This discipline is an unusual one in that it demands training that crosses most of the traditionally established intellectual boundaries.
A variety of factors make sex research especially challenging:
zz It can be difficult to obtain appropriate subjects to study. It’s easy enough to corral a classful of human sexuality students, but how representative are these of the general citizenry, let alone humanity as a whole? zz It can be difficult to phrase survey questions in ways that encourage hon-
est responses and that don’t bias responses to conform to researchers’ preconceptions. zz It can be difficult to extrapolate from animal research to human subjects. zz It can be difficult to obtain funding for research: Conservative politicians
have taken to vetting grant applications, looking for proposals that they can ridicule or defund. On the other hand, the epidemics of AIDS, herpes, and other sexually transmitted infections have led to the investment of a great deal of public and private funds into sex-related research topics.
Numerous organizations at local, international, and global levels now foster sex research. In the United States, the Society for the Scientific Study of Sexuality (SSSS, or “Quad-S”) publishes the Journal of Sex Research and other periodicals. The Ameri- can Association of Sexuality Educators Counselors and Therapists (AASECT) and the Society for Sex Therapy and Research (SSTAR) certify educational programs in sex education and therapy. There are also institutes devoted to research or training in issues of sexuality, such as the Kinsey Institute (which is affiliated with Indiana Uni- versity), and special-purpose organizations such as the Guttmacher Institute (which focuses on family planning issues).
At an international level, two organizations stand out. The International Academy of Sex Research publishes the Archives of Sexual Behavior. The World Association for Sexual Health, which represents sex-research and sexual-health organizations from
Prostitution is not the only sphere in which people calculate the value of sex and sexual relationships.
sexology The scientific study of sex and sexual disorders.
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53 countries, issued a universal Declaration of Sexual Rights in 1997, and it has been updated since that time. The 2014 declaration (in abridged form) is as follows:
zz The right to equality and non-discrimination zz The right to life, liberty, and security of the person zz The right to autonomy and bodily integrity zz The right to be free from torture and cruel, inhuman, or degrading treatment or
punishment zz The right to be free from all forms of violence and coercion zz The right to privacy zz The right to the highest attainable standard of health, including sexual health; with
the possibility of pleasurable, satisfying, and safe sexual experiences zz The right to enjoy the benefits of scientific progress and its application zz The right to information zz The right to education and the right to comprehensive sexuality education zz The right to enter, form, and dissolve marriage and other similar types of relation-
ships based on equality and full and free consent zz The right to decide whether to have children, the number and spacing of children,
and to have the information and the means to do so zz The right to the freedom of thought, opinion, and expression zz The right to freedom of association and peaceful assembly zz The right to participation in public and political life zz The right to access to justice, remedies, and redress
Summary zz Sexuality has changed over time, under the influence of evolution and culture. Certain modes of sexual behav- ior, such as competition for sex partners, were inherited from our nonhuman ancestors. The increasing conscious understanding of the connection between sex and repro- duction led to the development of efforts to interrupt the connection—by contraception and abortion.
zz The establishment of large-scale societies and govern- ments led to the regulation of sexuality. Marriage in particular has undergone many changes, from a contract arranged by men to a more voluntary and egalitarian arrangement that benefits both partners. The banning of polygamy by the early Christian church laid the ground- work for greater equality in marriage. Organized religion has often established moral codes that restrict sexual expression, especially nonreproductive behaviors such as sex between same-sex partners.
zz The steep reduction in the birthrate in many countries over the last two centuries has also allowed women to take a role in marriage that goes beyond incessant pregnancy and child rearing. Marriage itself has lost some of its significance in Western societies as nonmarital
cohabitation and child rearing, and at-will divorce, have become increasingly common and accepted.
zz Sexuality can be studied with a wide variety of approaches. The biomedical approach has been based primarily on studies in nonhuman animals, but recent advances, such as brain-scanning technology and the decoding of the human genome, allow for more direct study of sexual processes in humans.
zz The psychological approach falls into several subdisci- plines. Social psychology concerns itself with the diverse ways in which sex influences interpersonal relations. Cognitive psychology is focused on the mental processes, such as sexual arousal, that underlie sexual expression. Evolutionary psychology is devoted to understanding how evolutionary forces have molded our sex lives. Cul- tural anthropology investigates the influence of ethnic and cultural diversity on sexual expression.
zz Sociologists are concerned with the interactions between the sexuality of individuals and larger demographic groupings. Sex surveys are an important tool in this approach. An example of a theoretical social-science approach is sexual script theory: the notion that, as a
Go to the Discovering
Human Sexuality Companion Website at sites.sinauer.com/
discoveringhumansexuality3e for activities, study questions, quizzes, and other study aids.
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http://sites.sinauer.com/discoveringhumansexuality3e
Sexuality: pathwayS to underStanding 19
Discussion Questions 1. Do you think that the sexual behavior of nonhuman
animals has anything to teach us about what is morally acceptable in human sexual behavior?
2. How much does marriage or the prospect of marriage matter to you? Do you think men and women differ in how they view marriage?
3. What course of education would you recommend to someone who plans a career in sex research?
4. To what extent do you think that your religious upbring- ing and beliefs—or the lack of them—affect your cur- rent or future sexual and marital choices? If you’re not comfortable with this question, discuss how you believe college students should interpret the teachings of their religious leaders when making sexual decisions.
5. After reading the basics of the World Association for Sexual Health’s Declaration of Sexual Rights, do you agree with everything in it? Do you think the declara- tion fails to address any important topics? How would the principles laid out in the declaration bear on topics where there are marked differences between cultures, such as polygamy, female circumcision, prostitution, and homosexuality?
6. According to its mission statement, the Sexuality In- formation and Education Council of the United States (SIECUS) “advocates the right of individuals to make responsible sexual choices.” Should people also have the right to make irresponsible sexual choices? Where would you draw the line and on what grounds?
Web Resources American Association of Sex Educators Counselors and
Therapists (AASECT) www.aasect.org Archive for Sexology—English-language site at the
University of Berlin www2.hu-berlin.de/sexology Guttmacher Institute www.guttmacher.org International Academy of Sex Research (IASR)
www.iasr.org Kinsey Institute for Research in Sex, Gender, and
Reproduction www.kinseyinstitute.org
Sex Information and Education Council of Canada (SIECCAN) www.sieccan.org
Sexuality Information and Education Council of the United States (SIECUS) www.siecus.org
Society for Sex Therapy and Research (SSTAR) www.sstarnet.org
Society for the Scientific Study of Sexuality (SSSS) www.sexscience.org
Statistics Canada www.statcan.gc.ca World Association for Sexual Health (WAS)
www.worldsexology.org
Recommended Reading Ellis, H. (1900). Studies in the psychology of sex. Davis.
Freud, S. (1905/1975). Three essays on the theory of sexuality. Basic.
Kinsey, A. C., Pomeroy, W. B. & Martin, C. E. (1948). Sexual behavior in the human male. Saunders.
Kinsey, A. C., Pomeroy, W. B., Martin, C. E. & Gebhard, P. H. (1953). Sexual behavior in the human female. Saunders.
Krafft-Ebing, R. v. (1886/1999). Psychopathia sexualis, with special reference to contrary sexual instinct: A clinical-forensic study. Bloat.
Masters, W. H. & Johnson, V. E. (1966). Human sexual response. Little, Brown.
Masters, W. H. & Johnson, V. E. (1970). Human sexual inadequacy. Little, Brown.
Mead, M. (1928). Coming of age in Samoa: A psychological study of primitive youth for Western civilization. Morrow.
(The books listed above are historically important works but don’t necessarily represent current thinking.)
Dabhoiwala, F. (2012). The origins of sex: A history of the first sexual revolution. Oxford University Press.
Michael, R. T., Gagnon, J. H., Laumann, E. O. & Kolata, G. (1994). Sex in America: A definitive survey. Little, Brown.
Roach, M. (2008). Bonk: The curious coupling of science and sex. Norton.
Tolman, D.L. & Diamond, L.M. (Eds.) (2013). APA handbook of sexuality and psychology, Vols. 1 and 2. American Psychological Association.
result of constant interaction with others, people learn to play certain sexual roles. Sociologists also do ethno- graphic fieldwork in the environments where sexual transactions take place.
zz The economic approach to sexuality asks how the per- ceived costs and benefits of interactions within a sexual marketplace influence people’s sexual decision making.
zz Sexology, or sex research, is gradually asserting itself as an independent and multidisciplinary field of study. National and international organizations, conferences, and journals are devoted to the subject. The World Asso- ciation for Sexual Health has issued a universal Declara- tion of Sexual Rights.
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http://www.aasect.org
http://www.guttmacher.org
http://www.iasr.org
http://www.kinseyinstitute.org
http://www.sieccan.org
http://www.sexscience.org
http://www.statcan.gc.ca
http://www.worldsexology.org
http://www2.hu-berlin.de/sexology
2Chapter
Diversity in women’s vulvas. These life casts are among 400 that constitute The Great Wall of Vagina, by British artist Jamie McCartney.
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Women’s Bodies
Women and men are different, both in their bodies—the subject of this and the following chapters—and in their minds. Indeed, bodily differences, especially in the external genitals, are commonly used to decide whether a person is male or female. Yet many similarities and parallels exist between the bodies and minds of men and women—they are only variations on a common theme, after all. And there is considerable anatomical diversity within the categories of male and female. In fact, some babies are born with bodies that are not easy to categorize as either male or female, as we’ll discuss in Chapter 4.
By presenting women’s bodies first, we intentionally distance ourselves from the traditional perspective, which discussed women’s sex organs in terms of their equivalence to, or difference from, the sex organs of men. Neither men nor women are the “original” sex from which the other was molded: Women and men coevolved over millions of years from females and males of our ancestral species.
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22 chapter 2
A Woman’s Vulva Includes Her Mons, Labia, Vaginal Opening, and Clitoris Many girls and women have little understanding of their sexual anatomy, in part because the female external genitalia are not as prominent as those of men. In addi- tion, girls often learn that it’s not “nice” to inquire or talk about these body parts, or even to take a close look at them. Vague phrases such as “down there” may substi- tute for specific terms. Plenty of adult women—and men—do not know what the word “vagina” means and could not make a reasonable sketch of a woman’s genital anatomy. Thus, the “naming of parts” and the description of their layout is the crucial first stage of education in sexuality (Figure 2.1).
The word vulva is a scientific term that refers to the entire external genital area in a woman. The appearance of the vulva varies from woman to woman, a fact illustrated clearly in Figure 2.1B and in the body casts of 40 women pictured at the beginning of this chapter.
The mons is a pad of fatty tissue covered by skin and pubic hair. It lies immedi- ately in front of the pubic bone. The mons is erotically sensitive, and it may serve as a cushion for the woman’s pubic area during sex. The hair helps vaporize odors that arise in specialized sweat glands, similar to those in the armpits, and these odors may act as pheromones (chemical attractants). The mons with its pubic hair may also be a visual trigger for sexual arousal in a woman’s partner, since it is the most easily visible portion of the vulva.
external genitalia The sexual structures on the outside of the body.
vulva The female external genitalia. mons (or mons veneris) The
frontmost component of the vulva: a mound of fatty tissue covering the pubic bone.
pubic hair Hair that appears on portions of the external genitalia in both sexes at puberty.
Mons
(A)
(B)
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Clitoral hood Outer labia
Inner labia
Urethral opening
Vaginal opening
Clitoris
Vestibule
Perineum
Anus
Figure 2.1 The vulva, or female external genitalia. (A) Vulva with labia drawn apart to show the vestibule, urethral opening, and vaginal opening. The perineum and anus are not part of the vulva. (B) The inner labia are quite variable in shape and color from woman to woman. (See Web Activity 2.1: The Vulva.)
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women’s bodies 23
In spite of these possible functions for pubic hair, many women remove some or all of the hair by shaving, waxing, or other methods (Figure 2.2). Artistically expressive women may “vajazzle” the shaven area with sequins or crystals. Pubic hair removal is much more common among young women than among older women, according to a 2010 study by researchers at the Indiana University (Figure 2.3). However, the New York Times reports that some women are going back to the natural look, led by Hol- lywood actresses who either announced that they gave up hair removal or showed off their pubic hair in nude scenes (Meltzer, 2014). Many cultures (such as that of Japan) have viewed abundant pubic hair as highly erotic.
The labia (Latin for “lips”) are two pairs of skin folds that extend down from the mons on either side of the vulva. The outer labia, or labia majora, are padded with fatty tissue and are hairy on the surfaces nearest to the thighs. The skin of the outer labia is often darker than the skin elsewhere, and it is erotically sensitive, especially on the inner, hairless sides of the labia.
The inner labia, or labia minora, are two thin folds of hairless skin that lie between the two outer labia. In some women the inner labia are only visible after parting the outer labia; in other women they protrude to variable degrees (see Figure 2.1B). The inner labia meet at the back of the vulva, and also at the front, where they form the clitoral hood. The left and right inner labia generally touch each other in the mid- line when the woman is not aroused, and the area encircled by the labia is called the vestibule.
labia Two pairs of skin folds that form the sides of the vulva.
outer labia (or labia majora) Fleshy skin folds, partially covered in pubic hair, that extend from the mons.
inner labia (or labia minora) Thin, hairless folds of skin located between the outer labia and immediately flanking the vestibule.
clitoral hood A loose fold of skin that covers the clitoris.
vestibule The potential space be- tween the left and right inner labia.
Figure 02.02 DHS 3E LeVay Baldwin Sinauer Associates 09.25.14
(A) (B) (C)
Figure 2.2 Pubic hair—love it or loathe it? (A) Gustave Courbet’s 1866 painting The Ori- gin of the World put natural pubic hair front and center. (B) A Brazilian wax removes all pubic hair except a narrow strip. (C) Complete removal of pubic hair.
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Total removal Partial removal No removal
(A) (B)
Women age 18–24
Women age 40–49
58.5%
12.4%
29.1%
49.7%
27.8% 22.5%
Figure 2.3 Removal of pubic hair These charts compare hair removal practices in (A) young and (B) middle-aged women, based on a nonrandom survey of 2451 sexually active women. “Total removal” means that women were completely hairless at least once in the prior month. (After Herbenick et al., 2010d.)
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24 chapter 2
The inner labia are amply supplied with glands, blood vessels, and nerve endings and are very erotically sensitive. The appearance of the inner labia varies greatly from woman to woman. In some women they are virtually absent and are represented merely by slight ridges on the inner sides of the outer labia. In other women they extend well beyond the outer labia. In some cultures the inner labia are not left in their natural state, but are stretched, from childhood onward, with the aim of making the vulva more attractive. A small labia-stretching culture exists in the United States, too. Conversely, some women with naturally prominent or asymmetrical labia have them surgically reduced (Figure 2.4). During sexual arousal the inner labia swell and darken as they fill with blood, a process called vasocongestion.
When people use the word “labia” without any qualifier, they usually mean the inner labia.
There is more to the clitoris than meets the eye Within the vestibule are three important structures: the clitoris, the urethral opening, and the vaginal opening. The clitoris is a complex organ, only a portion of which is visible. The external portion is the clitoral glans, a small but highly sensitive knob of tissue positioned at the front of the vestibule. It is about the size of a pearl and, like a pearl, its size can vary. It is covered, or partly covered, by the clitoral hood but can be made visible by gently retracting the hood. The shaft of the clitoris, which is about 1 inch (2 to 3 cm) long, runs upward from the glans, under the hood. Although the shaft cannot be seen directly, it can be felt, and its outline may be visible through the skin of the hood. Both the shaft and the glans are erectile; that is, they are capable of becoming larger and firmer during sexual arousal. The erectile tissue within the clitoral shaft con- sists of two corpora cavernosa (“cavernous bodies”) that lie side by side. The erectile tissue within the glans consists of a single corpus spongiosum (“spongy body”).
Ointment-like secretions from the underside of the clitoral hood lubricate the motion of the hood over the clitoris, but when these secretions dry and mix with dead cells and bacteria, they form a pasty material called smegma, which can collect under the hood. Smegma may be removed, or prevented from accumulating, by pull- ing the clitoral hood back and gently washing the area with soap and warm water.
Two internal extensions of the clitoris, the crura, diverge backward and down- ward from the clitoral shaft, giving the entire clitoris a wishbone structure (Figure 2.5). The crura are about 3 inches (7 cm) long and partially enwrap the urethra. Yet another pair of structures, the vestibular bulbs, are closely associated with the clito- ris (O’Connell et al., 1998). They are curved masses of erectile tissue consisting of the same corpus spongiosum material that forms the clitoral glans. They surround the vestibule and underlie the inner labia. Like the crura, the vestibular bulbs are con- sidered to be internal portions of the clitoris. Erection of the vestibular bulbs during sexual arousal helps to lengthen and stiffen the vagina.
vasocongestion The swelling of tissue caused by an influx of blood.
clitoris The erectile organ in females, whose external portion is located at the junction of the inner labia, just in front of the vestibule.
glans The terminal knob of the clitoris or penis.
corpus cavernosum (pl., corpora cavernosa) Either of two elon- gated erectile structures within the clitoris or penis that also extend backward into the pelvic floor.
corpus spongiosum A single midline erectile structure. In both sexes, it fills the glans.
smegma A whitish, greasy secretion that builds up under the hood of the clitoris or the foreskin of the penis.
crura (sing. crus) The two internal extensions of the corpora cavernosa of the clitoris or penis.
vestibular bulbs Erectile structures beneath the inner labia, on either side of the vestibule.
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Figure 2.4 A woman’s vulva before and after surgical reduction of the inner labia (Courtesy of Dr. Robert H. Stubbs.)
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women’s bodies 25
The clitoris, especially the glans, is richly supplied with sensory nerve fibers whose function is to produce sexual arousal. Indeed, the only certain function of the clitoris is sexual pleasure, and its stimulation is the most reliable way for most women to experience orgasm. The clitoris is so sensitive that many women prefer diffuse or indirect stimulation rather than direct touching of the clitoris itself.
During sexual arousal, the clitoris swells and becomes erect: The shaft of the clitoris becomes firmer and more easily felt, but the glans remains soft. This is because a layer of tough connective tissue surrounds the shaft, restricting its expansion, whereas the glans is free to expand. The mechanism of erection is described in more detail in connection with the penis (see Chapter 3), where it has been studied in detail. The process of erection involves not just the shaft and glans, but also the deeper clitoral structures—the crura and vestibular bulbs (Suh et al., 2004). Typically, the glans of the clitoris is visible in the nonaroused state, but it may disappear under the clitoral hood during erection or with increasing sexual arousal, so sexual stimulation of the clitoris may occur through the hood rather than directly on the clitoral glans itself. Still, there’s quite a bit of variation from woman to woman in terms of her clitoral anatomy and what kind of clitoral stimulation she finds arousing. The clitoris is more erotically sensitive in the erect than in the flaccid state.
Not all women know that they have a clitoris or understand its function. Discus- sion of the clitoris can easily get skipped over in sex education classes, and plenty of women have never had a sex-ed class anyway. If they were discouraged, as girls, from exploring their bodies, and their partners have no particular interest in their sexual fulfillment, the structure may remain undiscovered.
On the other hand, in many societies or parts of societies, the clitoris gets quite a bit of attention. Piercing—usually of the clitoral hood but sometimes of the labia—is becoming an increasingly popular form of self-expression in the United States. It may be done for adornment, to enhance sexual stimulation, or even as a spiritual act. As with any genital piercing, scrupulous hygiene is required during the procedure as well as during the several-week healing period, in order to prevent infection and other potential complications (Dalke et al., 2013).
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Shaft
Hood
Glans Corpora cavernosa
Vestibular bulbs
Inner labia
Crura
Urethra
Vagina
Figure 2.5 Structure of the clitoris The inner labia are shown as if transparent. Both the clitoral glans and the vestibular bulbs are composed of corpus spongiosum tissue.
A vertical piercing of the clitoral hood—the most popular genital piercing in women.
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Female circumcision, also known as female genital cutting, is a traditional but highly controversial practice in some cultures. Cutting or removal of the external parts of the clitoris is a central element in female circumcision (Box 2.1).
Female Genital Cutting I was frozen with fear . . . I peered between my legs and saw the gypsy woman getting ready . . . I expected a big knife, but instead, out of the bag she pulled a tiny cotton sack. She reached inside with her long fingers, and fished out a broken razor blade . . . I saw dried blood on the jag- ged edge of the blade. She spat on it and wiped it against her dress. While she was scrubbing, my world went dark as my mother tied a scarf around my eyes as a blindfold. The next thing I felt was my flesh, my genitals, being cut away. (Dirie, 1998)
Like waris dirie, author of the foregoing account, an estimated 80 to 120 million women worldwide have been subjected to some form of cutting of their external genitals during childhood or puberty. the various procedures are referred to collectively as female circumcision, female genital cutting, or female geni- tal mutilation. the practice is prevalent in 29 countries, most of them in africa. eighty percent or more of the women in djibouti, egypt, eritrea, ethiopia, Gambia, sierra Leone, somalia, and sudan are believed to have been circumcised. Female geni- tal cutting is also practiced in the middle east, indonesia, and elsewhere (world health organization, 2010). it is particularly associated with islamic cultures, and although female circum- cision is not prescribed in the Quran, it is referred to favorably in later islamic texts and is often perceived to have religious significance.
there are three principal types of female genital cutting. in the least invasive version, known as sunnah, the clitoral hood is incised or removed. this procedure is roughly analogous to male circumcision as we know it in the United states (see box 3.1). in practice, however, some part of the clitoris itself is often removed during sunnah circumcision.
in the second procedure, known as clitoridectomy or exci- sion, the entire clitoral glans and shaft may be removed, along with the hood and sometimes nearby portions of the inner labia. the procedure varies according to local custom.
the third procedure, known as infibulation, is the most inva- sive. it is widely practiced in the sudan and somalia. (waris dirie is somali.) the procedure includes clitoridectomy but goes beyond it to include removal of the entire inner labia and the inner parts of the outer labia. the cut or abraded edges of the
two outer labia are then stitched together to cover the vestibule. only a small opening is left for the passage of urine and men- strual blood. when the woman first has coitus, the opening has to be enlarged—by forceful penetration with the penis or other object, or by cutting.
Female genital cutting is generally performed by traditional practitioners who lack medical training. it is often done with crude instruments and without anesthesia or attention to sani- tary conditions, so there is a risk of potentially fatal complica- tions, including hemorrhage and infection. there has been a recent trend toward the “medicalization” of the procedure— that is, its performance by trained medical personnel. this trend could reduce the rate of complications. the trend is controversial, however, since it may be seen as legitimizing the practice.
the long-term effects of female genital cutting are also con- troversial. in some cases, especially with infibulation, the pro- cedure can cause serious problems with urination, menstrua- tion, intercourse, childbirth, and fertility. but some studies have suggested that the harmful effects of the less-invasive forms of the practice have been exaggerated (shell-duncan & hernlund, 2000).
Waris Dirie from Somalia lifts up her World Social Award during the Women’s World Awards gala in Hamburg, Germany. Dirie has campaigned against the practice of female genital cutting.
Box 2.1 Society, Values, and the Law
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The appearance of the vaginal opening is variable The vaginal opening, or introitus, occupies the rear portion of the vestibule. In new- born girls, the vaginal opening is usually covered by a membranous fold of skin,
Female genital cutting may be done simply because it is a tradition in a given culture. a woman who retains her clitoris may be considered ritually unclean or dangerous to the health of a man who has sex with her. however, there may be a sec- ond purpose to the procedure: the reduction of female sexual activity, especially before or outside of marriage. this reduction is achieved either by decreasing the pleasure of sexual acts (especially by removal of the clitoris) or by making them painful or physically impossible (as with infibulation). in many cultures in which female genital cutting is practiced, a woman who has not undergone the procedure is not marriageable—which often means that she is condemned to a life of poverty.
in the United states, female circumcision has been illegal since 1996. significant numbers of immigrant women have been subjected to circumcision in their countries of birth, however, so western medical professionals need to be aware of the phe- nomenon. some circumcision of the daughters of immigrants does occur in the United states, but the prevalence of this illegal activity is hard to estimate. in 2010 the american academy of pediatrics (aap) floated the idea of legalizing the least invasive form of female genital cutting, in which the operator makes a nick or small cut in the clitoral hood. the suggestion met with a firestorm of opposition, and the aap eventually withdrew it (shweder, 2013).
the practice of female circumcision has been strongly con- demned by many americans on several grounds: that it is harm- ful and dangerous; that it interferes with women’s right to self- expression, especially in the sexual domain; that it subjugates women’s interests to the purported interests of men; and that it makes irreversible decisions for children before they are able to make those decisions for themselves.
in 2005 the african Union’s protocol on the rights of women in africa was ratified: it requires all 53 member states to pro- hibit female circumcision. this is a promising step, but its effect is uncertain. in egypt, for example, female circumcision has been illegal since 2007, but this has not led to any appreciable decrease in the practice. in fact, the 2011 overthrow of presi- dent hosni mubarak, whose wife was an ardent opponent of female circumcision, has been followed by an increase in its popularity (sharma, 2011).
although campaigning against female circumcision may seem like an entirely praiseworthy activity, it does potentially conflict with another value, namely, respect for cultural diver-
sity and autonomy. while we may be tempted to use words such as “mutilation” to describe female circumcision, women in the countries concerned have mostly positive views about the practice, and many girls want to have it done as a token of their womanhood and their membership in their culture. “why should i avoid the exercise when my mother and grandmother went through it?” said one 19-year-old Ugandan woman a year after that country banned the practice (magga, 2010).
it may be that the greatest progress will come from the work of activist organizations within the cultures concerned. such organizations now exist in many countries. one possible avenue for change is the institution of “ritual without cutting,” in which the traditional rites are preserved but the actual circumcision is omitted. the poster shown here was created by a Gambian organization dedicated to ending female genital mutilation and replacing the rite with one that does not involve cutting.
waris dirie now runs the desert Flower Foundation, which campaigns against genital cutting and supports girls and women who have undergone cutting.
female circumcision any of several forms of ritual cutting or excision of parts of the female genitalia.
sunnah Female genital cutting limited to incision or removal of the clitoral hood.
clitoridectomy removal of the entire external portion of the clitoris (glans, shaft, and hood).
infibulation the most invasive form of female genital cutting; involves removal of the clitoris, inner labia, and parts of the outer labia, plus the sewing together of the outer labia over the vestibule.
introitus The entrance to the vagina, usually covered early in life by the hymen.
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the hymen. The hymen has one or several openings that allow for menstrual flow after a girl begins to menstruate, and for the insertion of tampons (Figure 2.6). In a rare condition called imperforate hymen, this structure completely closes the vagi- nal opening (Adams Hillard, 2003). Imperforate hymen is often first diagnosed at puberty because it causes a blockage of menstrual discharge; it is treated surgically to create an opening through which the menstrual discharge can flow.
The hymen may tear or stretch when a woman first has sexual intercourse, which may lead to some pain and bleeding. This phenomenon has led to the traditional notion that the state of a woman’s hymen indicates whether or not she has ever engaged in coitus—that is, whether she is a virgin in one meaning of the term (see Chapter 10). One can certainly debate whether a woman’s virginity—or lack of it— should be a matter of concern to anyone besides the woman herself. In any case, the state of her hymen is not a reliable indicator of virginity. In some women the hymen undergoes changes at puberty that allow for intercourse without any tearing. Some women may have widened the opening during tampon use or athletic activities, or they may have deliberately stretched the opening with the intention of facilitating first intercourse.
In many Middle Eastern countries it is traditional for a bride’s mother or other relative to display the bloodstained sheets from a window after the bride’s wedding night, thereby proving to the community that the marriage was consummated and that the bride was indeed a virgin. Of course there may be no stain, for any number of reasons—the bride was not a virgin; she was a virgin but didn’t have an intact hymen; the couple achieved coitus without tearing of the hymen or without suf- ficient bleeding to stain the sheets; or they didn’t engage in coitus because the man ejaculated prematurely or because one or both parties were too anxious, too tired, or otherwise unable to perform the act. To guard against any of these possibilities, the mother may bring a vial of chicken blood with her.
In some Westernized regions of the Middle East, this ritual has become a light- hearted tradition. In more conservative communities, however, proof of a bride’s virginity is still so important that a woman who lacks an intact hymen may undergo an operation to reconstruct one before she marries (Bentlage & Eich, 2007).
The opening of the urethra is located between the vaginal opening and the clitoris. Given that the main function of the urethra is to pass urine, you might not consider
hymen A membrane, usually perforated or incomplete, that covers the opening of the vagina. It may be torn by first coitus or by other means.
imperforate hymen A hymen that completely closes the introitus.
urethra The canal that conveys urine from the bladder to the urethral opening.
(A) Annular hymen (B) Septate hymen
Clitoris
Urethral opening
Hymen
(C) Cribriform hymen (D) After childbirth
DHS 3E Figure 02.06
09/25/14
Figure 2.6 The hymen is highly variable in structure. Most commonly it is annular (A); that is, it has a round central opening that is large enough for passage of the menstrual flow and insertion of a tampon, but usually not large enough for coitus. (B) The opening may be crossed by a band of tissue (septate hymen) or (C) by several bands that leave numerous small openings (cribriform hymen). If the openings are very small, or are absent entirely (imperforate hymen), the outflow of vaginal secretions and menstrual fluids may be blocked. First inter- course often tears the hymen but leaves it partially intact. (D) Vaginal childbirth removes all but small remnants of the structure. Familiarity with variations in hymen structure is important for professionals who evaluate female sexual assault victims.
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it a sexual structure, but some women do ejaculate from it during sexual climax, as we’ll see shortly.
The perineum is the erotically sensitive area between the vaginal opening and the anus (or, in males, between the scrotum and the anus). Intestinal bacteria can be spread rather easily from the anus across the perineum to the vagina or urethra, which may cause a genital or urinary infection. For this reason, women are advised to wipe themselves in a backward, not a forward, direction after using the toilet.
Important structures underlie the vulva. We have already described the deep exten- sions of the clitoris. They are associated with various pelvic floor muscles, especially the pubococcygeus muscle (see Web Activity 2.2: Internal Anatomy of the Vulva). The steady contraction of these muscles stiffens the walls of the vagina during sex, thus increasing sexual sensations for both participants. These muscles, which contract more strongly at orgasm, increase pleasure, prevent urinary and fecal leakage, and possibly help to keep semen in the vagina. Exercises to increase the tone of the pubococcygeus muscle and other muscles of the pelvic floor (Kegel exercises) have been recommended for the treatment of sexual disorders as well as to prevent the involuntary leakage of urine or feces (incontinence). Kegel exercises are described in Chapter 14.
The Vagina Is the Outermost Portion of the Female Reproductive Tract As shown in Figure 2.7, the female reproductive tract, when viewed from the front, takes the shape of a capital letter T. The stem of the T is formed by the vagina, the cervix, and the body of the uterus. The two horizontal arms of the T are formed by the oviducts, also called fallopian tubes, whose ends are adjacent to the two ovaries. The reproductive tract serves the purpose of transport of the female’s eggs (ova) and the male’s sperm, as well as fertilization, pregnancy, and passage of the fetus during childbirth.
In a woman who is not sexually excited, the vagina is a collapsed tube that runs about 3 to 4 inches (8 to 10 cm) upward and backward from the vaginal opening. Penetration of the vagina by the penis constitutes coitus or sexual intercourse. The vagina plays a role in sperm transport and (along with the cervix) forms the birth canal through which a fetus reaches the outside world.
The vaginal wall is highly elastic and consists of three layers: a thin cellular lining, or mucosa; an intermediate muscular layer; and an outermost tough, elastic layer. The mucosa can be seen by parting the inner labia. When a woman is in a nonaroused state, it is pink in color. The vaginal wall has a series of folds that run around the circumference of the vagina.
The outer third of the vagina, near the vaginal opening, has a structure different from that of the internal portion (see Chapter 4). It is tighter, more muscular, and also more richly innervated than the deeper portion. Thus, most of the sensation during coitus—for both partners—derives from contact between the penis and this outer portion of the vagina.
The vagina is normally inhabited by large numbers of “friendly” bacteria that convert sugars to lactic acid. This bacterial activity usually makes the surface of the vagina mildly acidic (pH 4.0 to 5.0), and this helps to prevent the growth of harmful bacteria. The vagina also normally contains a variety of fungal organisms, especially Candida albicans. It sometimes happens that the fungal organisms overgrow, causing inflammation of the vaginal walls, itching, and possibly a thick white discharge. This condition is called candidiasis, vaginal thrush, or (in popular language) a “yeast infection.” The condition is diagnosed by microscopic examination of the discharge and is treated with antifungal medications. Some of these medications are available without a prescription. It is better to get a medical diagnosis, however, at least for the
perineum The region of skin be- tween the anus and the vulva or scrotum.
pelvic floor muscles A muscular sling that underlies and supports the pelvic organs.
pubococcygeus muscle A mus- cle of the pelvic floor that runs from the pubic bone to the coccyx (tailbone). In women it forms a sling around the vagina.
reproductive tract The internal anatomical structures in either sex that form the pathway taken by ova, sperm, or the conceptus.
vagina A muscular tube extending 3 to 4 inches (8 to 10 cm) from the vestibule to the uterine cervix.
coitus Penetration of the vagina by the penis.
sexual intercourse Sexual con- tact, usually understood to involve coitus.
birth canal The canal formed by the uterus, cervix, and vagina, through which the fetus passes during the birth process.
mucosa A surface layer of cells that is lubricated by the secretions of mucous glands.
candidiasis A fungal infection of the vagina. Also called thrush or a yeast infection.
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first episode, because women sometimes use over-the-counter medications for inap- propriate conditions, a practice that can lead to the development of drug-resistant infections (Centers for Disease Control, 2004). Though unpleasant, vaginal candidia- sis does not have serious health consequences. Persistent candidiasis can, however, be a sign of an underlying problem with the immune system.
One of the factors that can predispose women to candidiasis is frequent douch- ing—the rinsing of the vagina with a stream of water or other liquid as a “cleansing” or deodorizing procedure. Gynecologists discourage douching, because the vagina is usually a self-cleansing organ. A clear, odorless vaginal discharge is normal and does not require douching or any other treatment. Depending on the time of the menstrual cycle, the normal vaginal discharge may take on a whitish or yellowish appearance.
douche To rinse the vagina out with a fluid; the fluid so used.
Pelvic �oor muscles
Rectum
Anus
Perineum
Vagina
Clitoris
Pubic bone
Bladder
Uterus
Urethral opening
Vaginal opening
Cervix
(A) Midline view
DHS 3E Figure 0207
Paraurethral gland
Oviducts
Ovaries
Fimbria
Endometrium
Myometrium
Cervix
Os
Vagina
(B) Frontal view
Perimetrium
Figure 2.7 The female reproduc- tive tract (See Web Activity 2.3: The Female Reproductive Tract, Part 1 and Web Activity 2.4: The Female Reproductive Tract, Part 2.)
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If the discharge develops an unusual appearance or odor, however, this may be a sign of a sexually transmitted infection or of bacterial vaginosis. These conditions and their treatment are discussed in Chapter 15.
The vagina undergoes changes during arousal Like the inner labia, the walls of the vagina swell because of vasocongestion during sexual arousal. As a result, their color changes from pink to purple—the color of venous blood. One way that sex researchers monitor physiological arousal in women is to place a photocell in the vagina to track this color change (Figure 2.8). Vasoconges- tion of the vagina and inner labia, combined with the contraction of musculature in the vaginal walls and erection of the vestibular bulbs, cause the vagina to wrap more tightly around the penis during sexual intercourse than would otherwise be the case, which in turn increases sexual stimulation for both partners. For the woman, vaso- congestion of the inner labia facilitates motion of the clitoral hood and thus increases stimulation of the clitoris, the structure that is usually most erotically sensitive.
Another response of the vagina to arousal is lubrication. This involves a diffuse seepage of watery fluid through all parts of the vaginal mucosa. The fluid is made slippery by the addition of mucus secreted by glands in the cervix. Lubrication serves two functions. First, the lubricant has a near-neutral pH (neither acid nor alkaline), which offers a more sperm-friendly environment than the acidic pH of the nonaroused vagina. Thus, lubrication favors sperm survival and transport. Second, lubrication makes coitus and other stimulation of the vulva easier and more pleasur- able for both partners. This natural lubrication can be supplemented with the use of water-based “personal lubricants” if necessary.
The G-spot is a controversial erogenous zone Perhaps the most famous and controversial feature of the vagina is the Gräfenberg spot, or G-spot, named for the sexologist Ernst Gräfenberg, who described it in the early 1950s. Only a minority of women say they have a G-spot, but for those who do, it is an area of heightened sensitivity on the front wall of the vagina, about 1 to 2 inches (3 to 5 cm) from the vaginal entrance (Figure 2.9). Deep pressure at this location can first trigger the desire to urinate, but continued stimulation is sexually arousing and is said to trigger an orgasm that is different in quality from an orgasm caused by stimulation of the clitoris (Ladas et al., 2004).
What is the structural basis of the G-spot, if it exists? One can- didate is a set of paraurethral glands, which are located between the front wall of the vagina and the urethra (see Figure 2.7A). Their ducts open into the urethra. The female paraurethral glands and the male prostate gland are thought to develop from the same embryonic precursors (Zaviacic & Whipple, 1993). The paraure-
lubrication The natural appearance of slippery secretions in the vagina during sexual arousal, or the use of artificial lubricants to facilitate sexual activity.
Gräfenberg spot (G-spot) A possible area of increased erotic sensitivity on or deep within the front wall of the vagina.
paraurethral glands Glands situated next to the female urethra, thought to be equivalent to the prostate gland in males. Also known as Skene’s glands.
Clitoris
Anus
G-spot
Bladder
Uterus
DHs 3E Figure 02.09 Date 09.25.14
Figure 2.8 A photocell is used to measure female sexual arousal. It is placed against the vaginal wall and tracks the change in color as the tissues become engorged with blood.
Figure 2.9 Finding the G-spot The G-spot is said to be an area of heightened sen- sitivity on the front wall of the vagina. Not all women say they have a G-spot, and some sexologists question its existence altogether.
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thral glands could be the G-spot because, in some women, orgasms triggered by stimulation of this area are accompanied by ejaculation of fluid from the glands (see Chapter 5). Nevertheless, there has as yet been no clear identification of the G-spot with any anatomical structure (Kilchevsky et al., 2012; Hines & Kilchevsky, 2014).
Experts disagree vigorously about the existence or identity of the G-spot (Jan- nini et al., 2010). Some claim that every woman has a G-spot and that those who are unaware of its existence can be helped to identify it (Ladas et al., 2004). Others assert that the G-spot is a complete myth (Puppo, 2012). Debate about the G-spot is related to a controversy about vaginal versus clitoral orgasms, which we will consider in Chapter 5.
The Anus Can Also Be a Sex Organ Both heterosexual and homosexual couples may engage in penetration or manual or oral stimulation of the anus—anal sex (see Chapter 6), so the anus needs to be described along with the more obviously sexual structures. The anal orifice is located at the back of the perineum (see Figure 2.7A). It is kept tightly closed most of the time by contraction of the external and internal anal sphincter muscles. You can feel these sphincters by inserting your finger a short way into the anus. The external sphincter is under conscious control—you can squeeze down on your finger or release the ten- sion at will. The internal sphincter is not ordinarily under voluntary control; thus, it can cause problems during anal penetration. With experience a person can learn to relax this sphincter too.
Beyond the sphincters lies the rectum, the lowermost portion of the gastrointesti- nal tract. It is usually empty of feces except immediately before a bowel movement. The rectum is a much larger space than the anus, so most of the sensation generated during anal sex (for both partners) derives from penetration of the anus itself (which is both relatively tight and richly innervated), rather than from penetration of the rec- tum. In women, the structure in front of the rectum is the vagina. Stimulation of this and other nearby structures during anal sex may also contribute to sexual arousal.
The anus and rectum are lined by mucosa, but unlike the vaginal walls, this sur- face does not provide significant amounts of lubrication. Thus, most people who engage in anal sex use some type of lubricant. Other health concerns regarding anal sex are discussed in Chapter 6. Although we are postponing discussion of sexually transmitted infections (STIs) to Chapter 15, it’s worth mentioning now that condoms offer significant protection from STIs during anal sex, just as they do during vaginal sex.
The Uterus Serves a Double Duty The uterus or womb—the inward continuation of the female reproductive tract beyond the vagina—is a hollow organ that lies within the pelvic cavity (the portion of the abdominal cavity that is surrounded by the bones of the pelvis). In a nonpreg- nant woman the uterus is about the shape and size of a small upside-down pear (see Figure 2.7). The narrow part, the cervix, protrudes into the deep end of the vagina. A woman can feel her own cervix by inserting one or two fingers deeply into the vagina until she touches something that feels like the tip of her nose. She can see her cervix with the help of a mirror, a flashlight, and a speculum (an instrument that holds open the walls of the vagina; Box 2.2).
A constricted opening—the os—connects the vagina to a short canal that runs through the cervix. The cervical canal contains numerous glands that secrete mucus. The consistency and amount of this mucus change with the menstrual cycle, and this is why women experience changes in their vaginal discharge around the cycle.
anus The opening from which feces are released.
sphincter A circular muscle around a tube or orifice whose contraction closes the tube or orifice.
rectum The final, straight portion of the large bowel. It connects to the exterior via the anus.
uterus The womb; a pear-shaped region of the female reproductive tract through which sperm pass and where the conceptus implants and develops.
cervix The lowermost, narrow portion of the uterus that connects with the vagina.
os The opening in the cervix that connects the vagina with the cervical canal.
mucus A thick or slippery secretion.
What is “G-spot amplification”?
It’s a procedure, such as the injec- tion of collagen into the supposed region of a woman’s G-spot, that is claimed to amplify its function. The procedure hasn’t been shown to be effective or safe, and the American College of Obstetricians and Gynecologists strongly discour- ages it.
FAQ
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Near the time of ovulation its consistency is optimal for passage of sperm through the cervix.
The cervical canal opens into the cavity of the uterus proper. The wall of the uterus has three layers: an inner lining (endometrium), a muscular wall (myome- trium), and a thin, outer covering (perimetrium) that separates the uterus from the pelvic cavity, as shown in Figure 2.7B.
The endometrium must switch between two reproductive functions—the trans- port of sperm up the reproductive tract toward the site of fertilization, and the implantation and nourishment of an embryo. Because each of these two functions requires a very different organization, the structure of the endometrium changes
Genital Self-Examination if you’re a woman and you’ve never really taken a close look at your genital area, now may be a good time to do so.
Genital self-examination has several potential benefits. if you are reluctant or embarrassed to pay attention to your sexual anatomy, doing so in connection with this course may help you overcome these inhibitions and become more comfortable with your body. are there aspects of the way it looks that seem to you especially attractive, unattractive, or unusual, and if so, why? Vulvas differ greatly from woman to woman, especially in the distribution of pubic hair, the size and visibility of the clitoris, and the shape and color of the inner labia, but your anatomy is no more or less “normal” than any other woman’s. Finally, by becoming familiar with your vulva, you can more easily recog- nize any changes that may call for medical attention.
to get a good look at your vulva, you should use a hand mirror and possibly a flashlight (see Figure). Look while in a variety of postures and from a variety of angles. be sure you can recog- nize the parts that are described in the text. also, explore them with your fingers: what do they feel like to your fingers, and what do your fingers feel like to them? Use your fingers to gen- tly draw back the clitoral hood and to separate the labia, thus getting a view of the vestibule. if you become sexually aroused in the course of examining yourself, notice how the appearance of your vulva changes.
if you are curious to see the inside of your vagina and your cervix, you will need a flashlight and a vaginal speculum. this is a two-armed, “duck-billed” device made of plastic that holds the walls of the vagina apart. (a speculum can be obtained through women’s health organizations. they come in three sizes; a small is probably right unless you have reason to think you need a larger one.) First, wash the speculum and practice opening, locking, and unlocking it. then lubricate the speculum with a water-based lubricant (or just water). with your knees
apart, use the fingers of one hand to separate your labia. with the other hand, hold the speculum, with handle up and the twin arms closed, and slide it gently into your vagina. any discom- fort should be a signal to pause and relax, and if comfortable insertion isn’t possible, you should stop. once the speculum is fully in place, gently open and lock the arms, so that you now have both hands free to hold the mirror and flashlight. by shining the flashlight onto the mirror, you should be able to see your cervix, which looks like a rounded knob with a central hole or slit (the os). the appearance of the cervix varies around the menstrual cycle (due to changes in the cervical mucus) and from woman to woman. some women may see fluid-filled sacs on the cervix protruding through the os; these are usually harmless. to remove the speculum, first unlock and close the arms, then gently withdraw it. You should carefully wash the speculum with soap and water, rinse it, and put it away in a clean place. self-examination with a speculum helps a woman get to know her own body, but it isn’t a practical way to diag- nose medical problems or a substitute for regular professional checkups.
Box 2.2 Sexual Health
Genital self-examination. The white instrument is a speculum.
endometrium The internal lining of the uterus.
myometrium The muscular layers of the wall of the uterus.
perimetrium The outer covering of the uterus.
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over the menstrual cycle. A visible sign of this reorganization is menstruation—the shedding of part of the endometrial lining and its discharge, along with some blood, through the cervix and vagina.
The myometrium is composed primarily of muscles that are not under voluntary control. Involuntary contractions of the myometrium during labor play a vital role in delivery of the fetus. Myometrial contractions (often perceived as menstrual cramps) are also thought to aid in the shedding and expulsion of the endometrial lining at menstruation.
Cancer can affect the cervix or the endometrium Cancer of the cervix (cervical cancer) strikes about 13,000 American women annually and causes about 4400 deaths. The main factor predisposing women to cervical can- cer is infection with human papillomavirus (HPV), a virus that is sexually transmit- ted (see Chapter 15). Less important risk factors include chlamydia infection (Koskela et al., 2000), smoking, and immune system dysfunction.
The death rate from cervical cancer has dropped by about 75% since the 1950s. Much of this reduction can be attributed to the use of regular Pap tests—named for the pathologist George Papanicolaou (1883–1962), who developed the test. A Pap test is generally done as part of a pelvic examination. The American Cancer Society (ACS) recommends that women have Pap tests every 3 years between ages 21 and 30, every 5 years between ages 30 and 65, and no screening thereafter if previous tests have been negative (Saslow et al., 2012). There are more details about this in Chapter 15.
In a pelvic exam, the gynecologist or other health care provider first inspects the vulva for external problems and then uses a speculum to hold the walls of the vagina apart so that the vagina and cervix can be visually inspected for lesions, inflamma- tion, or a discharge. For the Pap test, a specially shaped wooden or plastic spatula is inserted while the speculum is in place, and a sample of cells and mucus is wiped from the cervix (Figure 2.10). To get a sample from the cervical canal, a small brush may be inserted into the cervical os.
The sample of cells and mucus taken from the cervix is spread on a slide and examined under a microscope. If the cells show precancerous changes, the health
menstruation The breakdown of the endometrium at approximately monthly intervals, with consequent loss of tissue and blood from the vagina.
Pap test The microscopic examination of a sample of cells taken from the cervix or (less commonly) the anus.
pelvic examination A visual and digital examination of the vulva and pelvic organs.
DHS3E_0210.ai LeVay Baldwin Dragon�y Media Group 10.08.14
Cervix
Swab
Speculum
Vagina
I’ve had the HPV vaccine. Do I still need Pap tests?
Yes, HPV vaccines don’t protect against all the types of HPV that cause cervical cancer.
FAQ
Figure 2.10 The Pap test A sample of cells is taken from the cervix. (See Web Activity 2.5: The Pap Test.)
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women’s bodies 35
care provider may proceed to a more-detailed examination of the cervix using an operating microscope. This procedure is called colposcopy. During the colposcopy, the provider may take biopsies or destroy precancerous lesions by freezing or other methods. Follow-up examinations are required to ensure that the lesions have not recurred.
A second sample may be taken at the same time to test for the presence of HPV— specifically, types of HPV that can cause cervical cancer (see Chapter 15). HPV testing is recommended for women age 30 and older (Centers for Disease Control, 2014j).
If a precancerous lesion escapes detection (most likely because the woman has not had a Pap test for several years, or has never had one), it may progress to true invasive cervical cancer. Symptoms of cervical cancer may include an abnormal, sometimes bloodstained vaginal discharge, pain during intercourse, or bleeding dur- ing intercourse. Of course, these symptoms are not specific to cervical cancer, but a woman who experiences them should see a doctor right away to ensure that if cancer is present, it is detected as soon as possible.
Endometrial cancer (often called uterine cancer) is three times more common than cervical cancer but causes only 50% more deaths. In other words, the survival rate is better for endometrial cancer: 90% of women diagnosed with early-stage endo- metrial cancer are still alive 5 years later (American Cancer Society, 2013c). A diagno- sis is usually made on the basis of cells or tissue removed from the uterus.
Except for the earliest-stage cervical cancers, cancers affecting the uterus are usu- ally treated by removal of the entire organ (hysterectomy). Sometimes other pelvic organs, such as the oviducts and ovaries, also have to be removed, depending on how advanced the disease is. Chemotherapy, radiation therapy, or a combination of both is commonly added to improve the woman’s chances of survival.
A full pelvic exam traditionally includes a “bimanual exam,” in which the health care provider inserts a gloved finger into the vagina and presses down on the abdo- men with the other hand. This allows the provider to feel the various pelvic organs. Because there are many false-positive findings that lead to unnecessary operations, increasing numbers of experts now believe that bimanual exams should be limited to women who have symptoms suggestive of a pelvic disorder (Brody, 2013).
Other uterine conditions include fibroids, endometriosis, abnormal bleeding, and prolapse Several noncancerous conditions are much more common than uterine cancer:
zz Fibroids are noncancerous tumors of smooth muscle that grow within or outside the uterus (Figure 2.11). They are very common: 20% to 25% of women develop them, usu- ally after the age of 30 but before menopause. They are often asymptomatic, but they can cause pain and abnormal bleed- ing. When fibroids do cause symptoms, they can be removed surgically or destroyed by blockage of the arteries that supply them with blood. If the woman does not want to have chil- dren in the future, hysterectomy is an option. zz Endometriosis is the growth of endometrial tissue at abnor-
mal locations within the pelvic cavity, such as on the oviducts, the ovaries, or the outside of the uterus. These patches of endometrial tissue are most likely derived from cells in the menstrual discharge that pass backward up the oviducts into the pelvic cavity, but other theories of causation have also been proposed. The most common symptom of endometriosis is pelvic pain; this pain may be worse before or during the
colposcopy The examination of the cervix with the aid of an operating microscope.
endometrial cancer Cancer of the endometrium of the uterus.
hysterectomy Surgical removal of the uterus.
fibroid A noncancerous tumor arising from muscle cells of the uterus.
endometriosis The growth of endometrial tissue at abnormal locations such as the oviducts.
(A) (B)
(D) (C)
Cervix
Endometrium
Myometrium
Stalk
DHS 3E Figure 03.11 09.25.14
Figure 2.11 Fibroids are noncan- cerous tumors of the uterus. They may be located on the endometrium (A), within the myometrium (B), or near the outer surface of the uterus (C). Some- times they are attached to the inner or outer surface of the uterus by stalks (D).
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menstrual period, or at the time of ovulation, or it may be ongoing. Endo- metriosis can cause infertility. There is no simple cure for the condition: Pain medications are helpful, as are oral contraceptives. Sometimes the patches of endometrial tissue can be removed surgically. zz Abnormal endometrial bleeding can be caused by some of the conditions
we have already discussed, but it can also occur for a variety of other reasons, or for no apparent reason at all. It can be treated with certain oral contraceptives, by surgery, or (if very persistent) by hysterectomy. zz Prolapse is a downward sagging of the uterus into the vagina. It is caused
by weakening of the ligaments that support the uterus and of the muscles of the pelvic floor. The condition is seen most often in elderly women who have had at least one child, because both aging and childbirth weaken the structures that support the uterus. Obesity and smoking are also risk fac- tors. Uterine prolapse may be treated by a variety of surgical techniques or by insertion of a plastic ring that keeps the uterus in place. Kegel exercises help to prevent uterine prolapse.
Should hysterectomy be so common? About 430,000 hysterectomies are performed in the United States annually (Wright et al., 2013b), and 1 in 3 women has had a hysterectomy by the age of 60. The associated costs exceed $5 billion annually. Medical research indicates that many hysterectomies are unneeded.
In a premenopausal woman hysterectomy puts an end to menstruation and ren- ders the woman infertile, but the operation does not have any hormonal effects unless it is accompanied by removal of the ovaries. Hysterectomy should not interfere with a woman’s enjoyment of sex or her ability to engage in coitus or experience orgasm. In some cases the cervix can be left intact, making it even less likely that there will be any impairment of the woman’s sexual pleasure. In this case, however, she will need to continue having regular Pap tests.
One study found that most women who have had a hysterectomy derive more pleasure from sex after the operation (Roovers et al., 2003). Women who undergo hysterectomy also report an improved general quality of life, and these improve- ments are greater than in women treated for the same conditions by nonsurgical means (Showstack et al., 2006).
Even so, the chances that a woman will undergo a hysterectomy are influenced by factors such as her race and the region of the country where she lives. This suggests that some hysterectomies are unnecessary. Women with noncancerous disorders of the uterus should be aware of the increasing range of options for treatment. Inpatient hysterectomy rates in the United States declined by 36% between 2002 and 2010 (Wright et al., 2013b).
The Oviducts Are the Site of Fertilization At the upper end of the uterus, the reproductive tract divides into two symmetri- cal branches, the oviducts (see Figure 2.7B), also called fallopian tubes or simply “tubes.” Each oviduct is about 4 inches (10 cm) long and forms a pathway between the uterus and the left or right ovary. Fertilization of an ovum by a sperm takes place in the outer third of an oviduct.
The interior surface of the oviducts is lined with cilia, microscopic hairlike struc- tures that wave in a coordinated fashion toward the uterus. Sperm moving from the uterus toward the ovary have to swim against the current set up by the beating cilia,
prolapse The slipping out of place of an organ, such as the uterus.
oviduct Either of two bilateral tubes that lead from the uterus toward the ovaries, the usual site of fertilization. Also called a fallopian tube.
cilia Microscopic, hairlike extensions of cells, often capable of coordinated beating motions.
If hysterectomies are unnecessary why are they
done?
Some are necessary. Some are not strictly necessary but do relieve pain or bleeding. Some are done because women are unaware of alternative treatments or their doctors are not trained to provide them..
FAQ
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rather like salmon swimming upstream, but this current is too slow to offer a serious impediment to healthy, fast-moving sperm.
The portion of each oviduct near the uterus is relatively narrow, but it widens somewhat as it nears the ovary. The oviduct ends in a flared opening with a fringe composed of fingerlike extensions. This fringe is known as a fimbria. Each fimbria lies near, but is not actually fused with, the ovary on that side of the body. Like the rest of the two oviducts, the left and right fimbrias are lined with cilia that help draw the ovum into the oviduct.
A continuous pathway extends from the outside of a woman’s body, up her repro- ductive tract, and into the pelvic cavity. The body has many mechanisms to prevent disease-causing organisms from migrating up this pathway: For example, the pres- ence of mucus in the cervix acts like a plug, hindering the passage of microorganisms. In some circumstances, however, sexually transmitted organisms can travel part or all of the way up the pathway, causing inflammation in the reproductive tract or even within the pelvic cavity. This kind of infection is known as pelvic inflamma- tory disease (PID).
The Ovaries Produce Ova and Sex Hormones The ovaries—a woman’s gonads—are paired organs located on either side of the uterus. They are egg-shaped structures measuring about 1 to 1.5 inches (3 cm) long. A woman’s ovaries and a man’s testicles are about the same size and shape.
Under the microscope, an adult woman’s ovary can be seen to contain a large number of follicles at various stages of development (Figure 2.12). Each follicle con- sists of an ovum, or egg cell, surrounded by fluids and supporting cells.
The ovaries have two distinct functions. The first is to release ova in a process called ovulation. A newborn female has about a million undeveloped ova in each ovary, but these numbers decline throughout life. By puberty a woman has about 200,000 ova in each ovary. During her reproductive life she typically releases only one mature ovum per menstrual cycle. Thus, only a tiny fraction of a woman’s ova are actually ovulated during her lifetime. Much greater numbers of ova die and are reabsorbed by the body.
fimbria The fringe at the end of the oviduct, composed of fingerlike extensions.
pelvic inflammatory disease (PID) An infection of the female reproductive tract, often caused by sexually transmitted organisms.
ovary The female gonad; the organ that produces ova and secretes sex hormones.
gonad An organ that produces ova or sperm and secretes sex hormones.
follicle A fluid-filled sac that contains an egg (ovum), with its supporting cells, within the ovary.
ovum (pl. ova) A female gamete, or egg.
ovulation Release of an ovum from an ovary.
(A) (B)
Follicles Ovum CavitySupporting cells
DHS 3E Figure 02.12 09/25/14
Figure 2.12 Microscopic structure of the ovary (A) Ovarian follicles. Low-power view of an ovary, showing a number of follicles. (B) Higher-power view of a single follicle, showing the central cavity and the ovum surrounded by supporting cells.
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The second function of the ovaries is the production and secretion of sex hormones (Table 2.1). These sex hormones regulate the monthly menstrual cycle (Box 2.3). The ovarian hormones are mostly sex steroids, which are fatty molecules derived from
sex steroid Any of the steroid hormones that are active in sexual and reproductive processes.
The Feedback Loop that Controls Female Hormone Production ovulation and hormone secretion are regulated by a three- segment control loop that involves the passage of hormones between the brain, the pituitary gland, and the ovaries (see figure). First, a small region at the base of the brain named the hypothalamus secretes gonadotropin-releasing hormone (GnRH) into local vessels that carry it to the nearby pituitary gland. there it activates cells that manufacture and secrete two more hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). because these two hormones act on the gonads (in women, the ovaries), they are named gonado- tropins, meaning gonad-influencing substances. second, these two hormones enter the general blood circulation and reach their targets, the ovaries. Fsh, as its name suggests, stimu- lates the development of ovarian follicles to the point that they are capable of ovulation. Lh triggers ovulation itself, and it also causes the release of sex steroids by the ovaries. in the third segment of the loop, ovarian hormones pass via the general cir- culation system to the hypothalamus and pituitary gland, where they influence the release of Gnrh, Fsh, and Lh. this feedback influence is inhibitory at low estrogen levels but switches to stimulation at high levels. as described later in the chapter, the switch occurs late in the preovulatory phase of the menstrual cycle and is a key trigger for ovulation.
pituitary gland a gland under the control of and situated below the hypothalamus; its anterior lobe secretes gonadotropins and other hormones.
hypothalamus a small region at the base of the brain; it contains cells involved in sexual responses and other basic functions.
gonadotropin-releasing hormone (GnRH) a hormone secreted by the hypothalamus that stimulates the release of gonadotropins from the anterior pituitary gland.
follicle-stimulating hormone (FSH) one of the two major gonadotropins secreted by the pituitary gland; it promotes maturation of ova (or sperm in males).
luteinizing hormone (LH) one of the two major gonadotropins secreted by the pituitary gland; it triggers ovulation and promotes the secretion of sex steroids by the ovaries (or testicles).
gonadotropins hormones that regulate the function of the gonads.
BOX 0203 DHS 3E Sinauer Associates 09.25.14
Ovary
Hypothalamus
Progestins Androgens
Uterus, breasts, and other organs
Anterior pituitary
Inhibition (red) at low levels
Stimulation (blue) at sustained high levels
Estrogens
LHFSH
GnRH
The hypothalamus in the brain sends signals to the pituitary gland. In response to these, the pituitary releases FSH and LH that affect the ovaries. At different times in the menstrual cycle, the ovaries produce various mixes of estrogens, pro- gestins, and androgens. These affect the uterus, breasts, and other organs differently across the cycle. (See Web Activity 2.6: Ovarian and Uterine Cycles.)
Box 2.3 Biology of Sex
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TABLE 2.1 Principal Sex Hormones and Their Actions
Class/subclass of hormone Name Site of production Main targets Main hormonal actions
SEX STEROIDS
Estrogens Estradiol Gonads Widespread in body and brain
Feminizes body at puberty; contributes to menstrual cycle; increases density of bone; ends growth of limb bones at puberty; feedback inhibition of gonadotropins; maintains sex drive (?)
Androgens Testosterone Gonads, adrenal cortex
Widespread in body and brain
Masculinizes body and brain during fetal development and at puberty; anabolic effects; maintains sex drive; feedback inhibition of gonadotropins
5α-Dihydro- testosterone (DHT)
External genitalia, prostate gland, skin (converted from testosterone)
External genitalia, prostate gland, skin
Development and maintenance of male external genitalia and prostate gland; adult male patterns of hair distribution
Progestins Progesterone Ovary (corpus luteum), placenta
Uterus Contributes to menstrual cycle; maintains pregnancy
PROTEINS/PEPTIDES
Releasing hormones Gonadotropin-releasing hormone (GnRH)
Hypothalamus Anterior lobe of pituitary gland
Causes release of gonadotropins
Follicle-stimulating hormone (FSH)
Anterior lobe of pituitary gland
Gonads Stimulates maturation of ovarian follicles; stimulates spermatogenesis
Gonadotropins Luteinizing hormone (LH)
Anterior lobe of pituitary gland
Gonads Stimulates secretion of gonadal steroids; stimulates ovulation
Human chorionic gonadotropin (hCG)
Conceptus Ovary Maintains corpus luteum
Prolactin Anterior lobe of pituitary gland
Breast Prepares breast for lactation
Growth hormone Anterior lobe of pituitary gland
Widespread in body
Stimulates growth spurt at puberty
Other Inhibin Gonads Anterior lobe of pituitary gland
Feedback inhibition of gonadotropin secretion
Oxytocin Hypothalamus (transported to posterior pituitary for secretion)
Breast, uterus Milk letdown; uterine contractions during labor; role in orgasm (?); other nonreproductive functions
Anti-Müllerian hormone (AMH)
Developing testes Müllerian duct Causes regression of Müllerian duct during male fetal development
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cholesterol. The sex steroids come in three classes: estrogens (of which the main representative is estradiol), progestins (main representative: progesterone), and androgens (main representative: testosterone).
Both the female gonads (ovaries) and the male gonads (testicles) make all three classes of sex steroids, but in differing amounts. The ovaries secrete relatively large quantities of estrogens and progestins, which are therefore sometimes thought of as “female hormones.” The ovaries secrete relatively small quantities of androgens, but these small amounts are supplemented by androgens from another source, the adrenal glands, which lie on top of the kidneys.
Several medical conditions can affect the ovaries. The most significant is ovarian cancer, which is not a particularly common form of cancer: It strikes about 22,000 American women annually. Risk factors for ovarian cancer include older age (the median age at diagnosis is 65), a family history of the disease, possession of cancer- promoting genes, early onset of menstruation (menarche), late menopause, not hav- ing children, obesity, and prolonged hormone replacement therapy. The use of oral contraceptives for more than 5 years decreases the risk of ovarian cancer by about 60%.
Early ovarian cancer is usually asymptomatic, and no screening tests have been shown to reduce mortality in average-risk women. Women with a family history of ovarian cancer can be tested for the possession of cancer-causing genes—dam- aged versions of BRCA1 and BRCA2—which are the same genes that cause breast cancer, discussed later in the chapter. Typically, ovarian cancer makes itself known by abdominal swelling, a constant feeling of a need to urinate or defecate, diges- tive problems, or pain in the pelvis, back, or leg. The accuracy of diagnosis can be improved by measuring blood levels of a marker known as CA-125 (Gordon, 2008). Treatment typically involves surgery to remove as much of the tumor as possible, as well as chemotherapy. Often the cancer has spread beyond the ovary by the time of diagnosis; thus, the survival rate is low: Only about 1 in 2 women survives for 5 years.
Another condition affecting the ovaries is the presence of ovarian cysts (fluid- filled sacs). These may be discovered when they cause pain, or they may be diag- nosed during a pelvic exam. In women of reproductive age, the cysts are usually normal ovarian follicles that have not yet ovulated or that have grown larger than usual. These usually regress without treatment. Nevertheless, cysts can also be a sign of cancer, especially when found in prepubescent girls or in postmenopausal women.
Polycystic ovary syndrome (PCOS) is a common but poorly understood condi- tion in which the ovaries secrete high levels of androgens. The condition may cause irregular menstruation, infertility, and a male-like pattern of facial and body hair. Ovarian cysts are often, but not always, present. PCOS is not curable, but most of the symptoms can be controlled with contraceptive pills or other drugs.
Menstruation Is a Biological Process with Cultural and Practical Aspects The menstrual cycle has one obvious external sign: menstruation, also known as menses, a menstrual period, or simply a period. This is the vaginal discharge of endo- metrial tissue and blood that women experience at approximately monthly intervals during their fertile years. It is brought about by a complex internal mechanism that involves the ovaries, the brain, the pituitary gland, and the uterus.
The length of the menstrual cycle varies greatly among women and can also vary from one cycle to the next in the same woman. Most women have cycles lasting between 24 and 32 days, but cycles as short as 20 days or as long as 36 days are not unusual or unhealthy. Cycle length tends to be irregular for several years after the cycles first begin at puberty. Health care providers should ask teenage girls about
estrogens Any of a class of steroids—the most important being estradiol—that promote the development of female secondary sexual characteristics at puberty and that have many other functions in both sexes.
estradiol The principal estrogen, secreted by ovarian follicles.
progestins Any of a class of steroids, the most important being progesterone, that cause the endometrium to proliferate and help maintain pregnancy.
progesterone A steroid hormone secreted by the ovary and the placenta; it is necessary for the establishment and maintenance of pregnancy.
androgens Any of a class of steroids—the most important being testosterone—that promote male sexual development and that have a variety of other functions in both sexes.
testosterone The principal androgen, synthesized in the testicles and, in lesser amounts, in the ovaries and adrenal glands.
menarche (Pronounciations vary; MEN-ar-kee is most common.) The onset of menstruation at puberty.
ovarian cysts Cysts within the ovary that can arise from a number of different causes.
polycystic ovary syndrome (PCOS) A condition marked by excessive secretion of androgens by the ovaries.
Can a woman menstruate during pregnancy?
No, but many women experience some light vaginal bleeding early in pregnancy—for example, as the conceptus implants in the uterus. Major bleeding, bleeding accompa- nied by pain, or any bleeding after the first trimester are reasons to see your doctor promptly.
FAQ
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their menstrual cycles, both in order to provide information and reassurance, and to identify problems needing medical attention (American Academy of Pediatrics, 2006). Cycles are also irregular at the approach of menopause. Menstrual cycles cease during pregnancy and, to a less predictable degree, during the time when a mother is breast-feeding her infant. It has been claimed that the menstrual cycles of women who live together tend to synchronize, but some researchers have contested the real- ity of this phenomenon (Box 2.4).
Menstrual Synchrony: Reality or Myth? do women who live together get their periods at the same time? anecdotal accounts have long sug- gested that they do, but scientific evidence was lacking until 1970. in that year martha mcclintock, then a student at wellesley college, decided to investigate the matter. her results ignited a scien- tific controversy that still rages.
mcclintock kept records of the menstrual peri- ods of the students in her dormitory. she reported that, over the course of a semester, the periods of women who spent a lot of time together occurred closer and closer in time. her analysis (mcclintock, 1971) appeared to give “menstrual synchrony” sci- entific grounding.
what’s more, her findings resonated with the spirit of 1970s feminism. here was a biological expression of solidarity among women—a sisterhood that men knew nothing about and could never join. before long, menstrual synchrony became common knowledge—something that most people had heard about and probably believed.
Yet the existence of menstrual synchrony remains highly controversial. although some studies seem to support mcclintock’s claims, at least in part (weller et al., 1995; weller & weller, 1997), other researchers have failed to detect synchrony, even in circumstances very similar to those of mcclintock’s original study, or have found methodological problems in the studies that do claim to find synchrony (arden & dye, 1998; Yang & schank, 2006). two groups of research- ers failed to find any menstrual synchrony between cohabiting lesbian couples, who one might imagine would be the most likely to synchronize (trevathan et al., 1993; weller & weller, 1998). and recent studies have failed to observe menstrual synchrony among nonhuman primates (Furtbauer et al., 2011; setchell et al., 2011).
one of the most vocal critics of mcclintock’s work is anthro- pologist beverly strassmann (strassmann, 1997, 1999). stras- smann studied the dogon, a traditional west african people who have the custom of sending menstruating women to a “menstrual hut” (see box 2.5). because of this practice, it was easy for stras- smann to keep track of the menstrual periods of all the women in the community. she never observed synchronization of cycles, even between women who were sisters or close friends.
mcclintock herself remains adamant that the phenomenon of menstrual synchrony exists, and she claims to have discov- ered its mechanism—pheromones released by women that supposedly affect the timing of menstruation in other women who receive these chemical signals (mcclintock, 1999). still, mcclintock is willing to admit that the phenomenon may be a lot more complicated than she originally thought. sometimes women synchronize, she says, sometimes they desynchronize, and sometimes they just remain random.