Gay, Straight, and the Reason Why: the Science of Sexual Orientation/Simon Levay

Gay, Straight, and the Reason Why < This page intentionally left blank Gay, Straight, and the Reason Why The Science of Sexual Orientation SIMON LeVAY 1 2011 1 Oxford University Press, Inc., publishes works that further Oxford University’s objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Copyright © 2011 by Simon LeVay Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data LeVay, Simon. Gay, straight, and the reason why: the science of sexual orientation/Simon LeVay. p. cm. Includes bibliographical references and index. ISBN 978-0-19-973767-3 1. Sexual orientation. 2. Sex (Psychology) 3. Sex (Biology) I. Title. BF692.L476 2010 155.3–dc22 2009049210 1 3 5 7 9 8 6 4 2 Printed in the United States of America on acid-free paper CONTENTS - Introduction vii one What Is Sexual Orientation? 1 two Why We Need Biology 27 three The Outline of a Theory 45 four Childhood 73 five Characteristics of Gay and Straight Adults 97 six The Role of Sex Hormones 129 seven The Role of Genes 157 eight The Brain 191 VI S CONTENTS nine The Body 221 ten The Older-Brother Effect 247 eleven Conclusions 271 Glossary 297 Notes 309 Bibliography 331 Author Index 393 Subject Index 397 INTRODUCTION - n August 1991, when I was a neuroscientist working at the ISalk Institute for Biological Studies in San Diego, I published a short research paper in the journal Science. The article was titled “A difference in hypothalamic structure between het- erosexual and homosexual men.” It attracted a great deal of interest from the media, the general public, and the scientifi c community, and it helped trigger a wave of new research into an age-old question: What makes people straight or gay? The hypothalamus* is a small region at the base of the brain that helps regulate several of our instinctual drives, including * Most technical terms are italicized at fi rst mention and are defi ned in the Glossary, starting on page 297. VII VIII S INTRODUCTION our sex drive. In my study, I took specimens of the hypothalamus from men and women who had died and were undergoing autopsy. About half of the men were gay. I focused on a region at the front of the hypothalamus that is known to be involved in regulating the sexual behaviors typically shown by males. Within this region lies a rice-grain-sized collection of nerve cells named INAH3, which is usually larger in men than in women. I confi rmed this basic sex difference. In addition, how- ever, I found that INAH3 was signifi cantly smaller, on average, in the gay men than in the straight men. In fact, there was no difference in size between INAH3 in the gay men and the women in my sample. I interpreted this fi nding as a clue that biological processes of brain development may infl uence a man’s sexual orientation. I was certainly not the fi rst person to have thought about sexual orientation from a biological perspective. A hundred years ago, a German physician and sex researcher, Magnus Hirschfeld, proposed that brain development followed different paths in fetuses destined to become gay adults and those destined to become straight. Just a year before I published my study, a Dutch group reported that another cluster of cells in the hypothalamus, the suprachiasmatic nucleus, also differed in size between gay and straight men. And, during the mid 1980s, psy- chiatrist Richard Pillard of Boston University had reported evidence that homosexuality clustered in certain families, raising the possibility that genes running in those families might be infl uencing the sexual orientation of family members. INTRODUCTION s IX But my report differed in signifi cant respects from most earlier ones. For one thing, by studying a brain region that is known to help regulate our sexuality I was, perhaps, cutting closer to the heart of the matter than earlier studies had done. Also, many of the earlier studies had talked about homosexuality as if it was an abnormality or problem, while heterosexuality was something so normal that it barely needed to be mentioned. The Dutch researchers, for example, had titled their study “An enlarged suprachiasmatic nucleus in homosexual men”—as if gay men had some kind of pathological swelling or tumor in that part of their brains. I doubt that the Dutch researchers actually thought about the matter in that way. Still, by titling their study as they did they fostered a point of view that has been all too prevalent over the years—a point of view that could be summarized in the question: What’s wrong with gay people? There’s nothing wrong with gay people. I’m gay myself, and happy to be so. There are some differences between us and the rest of humanity, certainly, as I’ll discuss in this book. Some of these differences are trivial, and some may infl uence people’s lives in interesting ways, making being gay or straight more than just a matter of “who we love.” But pathology doesn’t come into it. Whatever the exact reason, my 1991 study received a lot more attention from the media, and from the public at large, than had earlier studies. On the day of publication, most of the leading U.S. newspapers carried front-page stories about it. Because I was home-town talent, the San Diego Union-Tribune actually gave my report top billing, relegating what was probably X S INTRODUCTION a more signifi cant news item on that day—the collapse of the Soviet Union—to a humbler position on the page. Gay people reacted more favorably to my report than they had done to earlier studies. Some gay academics did exhibit a certain hostility—I recall psychologist John De Cecco of San Francisco State University denouncing it as “another example of medical homophobia” in a television interview. More com- monly, though, gay people told me that my fi nding validated their own sense of being “born gay” or being intrinsically different from straight people. This they perceived as a good thing, because people with anti-gay attitudes often portray homosexuality as a lifestyle or a choice that people make—and by implication a bad choice. My own position is this: The scientifi c knowledge currently available does bolster the idea that gays and lesbians are distinct “kinds” of people who are entitled to protection from discrim- ination, especially by governments, rather in the same way that racial minorities are. But I also believe that there would be plenty of reasons why gay people should be accepted and valued by society, even if being gay were proven to be an outright choice. I wrote extensively about the social implications of this kind of research in my earlier book, Queer Science,1† so I will not revisit that theme here, except for a few closing remarks. Rather, my intent in the present book is simply to give some idea of where the science stands today, 19 years after my Science paper appeared. † Endnotes begin on page 309, and consist of literature references only. INTRODUCTION s XI That paper was followed by a welter of new research. Not by myself, because I left my position at the Salk Institute in 1992. Since then, I have occupied myself as a writer and teacher, but I have maintained a close interest in the fi eld that I had worked in. Much of the new research has been done by a younger generation of scientists—neuroscientists, endocrinologists, geneticists, and cognitive psychologists—in laboratories across the United States, in Canada, Britain, and several European countries. My study, and the publicity it generated, helped trigger much of this new work, but it certainly wasn’t the whole inspiration. Richard Pillard, for example, along with psychologist Michael Bailey of Northwestern University, published an important genetic study on sexual orientation in late 1991, just a few months after my Science paper appeared. Their study had been completed before my paper came out and was in no way infl u- enced by it. Pillard and Bailey’s work led to further studies by their own research groups, and it helped draw molecular geneticists and other specialists into the fi eld. Taken together, the multitude of research studies published since 1991 have greatly strengthened the idea that biological factors play a signifi cant role in the development of sexual orientation—in both men and in women. More than that, they tend to bolster a particular kind of biological theory. This is the idea that the origins of sexual orientation are to be sought in the interactions between sex hormones and the developing brain. These interactions are what predispose our developing minds XII S INTRODUCTION toward some degree of “masculinity” or “femininity.” In other words, this theory places sexual orientation within the larger framework of gender—the collection of psychological traits that differ between the male and female sexes—but gender as seen from a very biological perspective.

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