Discovering human sexuality 3rd edition ebook

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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: publish@sinauer.com 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:publish@sinauer.com
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.