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What causes a child to grow up gay or straight? In this book, neuroscientist Simon LeVay summarizes a wealth of scientific evidence that points to one inescapable conclusion: Sexual orientation results primarily from an interaction between genes, sex hormones, and the cells of the developing body and brain.LeVay helped create this field in 1991 with a much-publicized study in Science, where he reported on a difference in the brain structure between gay and straight men. Since then, an entire scientific discipline has sprung up around the quest for a biological explanation of sexual orientation. In this book, LeVay provides a clear explanation of where the science stands today, taking the reader on a whirlwind tour of laboratories that specialize in genetics, endocrinology, neuroscience, cognitive psychology, evolutionary psychology, and family demographics. He describes, for instance, how researchers have manipulated the sex hormone levels of animals during development, causing them to mate preferentially with animals of their own gender. LeVay also reports on the prevalence of homosexual behavior among wild animals, ranging from Graylag geese to the Bonobo chimpanzee. Although many details remain unresolved, the general conclusion is quite clear: A person's sexual orientation arises in large part from biological processes that are already underway before birth. LeVay also makes it clear that these lines of research have a lot of potential because--far from seeking to discover "what went wrong" in the lives of gay people, attempting to develop "cures" for homosexuality, or returning to traditional explanations that center on parent-child relationships, various forms of "training," or early sexual experiences--our modern scientists are increasingly seeing sexual variety as something to be valued, celebrated, and welcomed into society.
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G a y, S t raigh t , and the Re ason W h y
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Gay, Straight, and th e
R e ason Why T he Scie n c e o f S e x u a l Or ient at io n
S I M O N L e VAY
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 o ne
Wh a t Is Sexual Orienta ti o n? 1 two
W hy We Need Biolog y 27 thre e
T h e Outline of a Theor y 45 fo u r
Childhood 73 five
C h a racteristics of Gay and Straight Adults 97 s ix
T h e Role of Sex Hormones 129 s e ve n
T he Role of Genes 157 e igh t
The Brain 191
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