Straight Science?: Homosexuality, Evolution and Adaptation

236 Pages·1997·1.55 MB·English

by  Jim McKnight

Straight science?
Homosexuality is a problem for evolutionary theory. How does a non-
reproductive sexual preference survive? There is increasing evidence for a
biological basis to homosexuality, not least the discovery in 1993 of markers
for a gay gene. Yet Darwinism, the most widely accepted evolutionary
theory, emphasises successful reproduction and the ‘survival of the fittest’.
How do we explain a lifetime preference for non-reproductive sex? What
does evolutionary theory make of a behaviour that seems to be positively
selected yet produces fewer children? Surely homosexuality defies
evolutionary explanation? Is there an evolutionary advantage to
homosexuality? Straight Science? examines the latest research and considers
these questions from an evolutionary perspective.
While social constructivism offers explanations in terms of social learning
and cultural preferences, the body of evidence for a genetic predisposition to
homosexuality grows. The implication of adopting the social constructivist
view of homosexual sex is that such sex is merely misdirected and therefore
futile, but far from dying out it continues through the ages and across
cultures.
Jim McKnight provides a comprehensive summary of the research on the
biology of homosexuality, including twin studies; hormonal assays;
anatomical, functional and molecular biology differences; and the search for
a gay gene. The book considers biological and social evolutionary theories of
the causation of homosexuality, and puts forward a model of the most likely
causes. It concludes with an overview of the adequacy of social
constructivist challenges to a biosocial perspective on homosexuality.
Jim McKnight is Chair of the Psychology Department at the University of
Western Sydney, Macarthur, and author of six books including Social
Psychology (1994) (with J.E.Sutton).
Straight science?
Homosexuality, evolution and
adaptation
Jim McKnight
London and New York
First published 1997
by Routledge
11 New Fetter Lane, London EC4P 4EE
This edition published in the Taylor & Francis e-Library, 2005.
“To purchase your own copy of this or any of Taylor & Francis or Routledge’s
collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.”
Simultaneously published in the USA and Canada
by Routledge
29 West 35th Street, New York, NY 10001
© 1997 Jim McKnight
All rights reserved. No part of this book may be reprinted or reproduced or utilised
in any form or by any electronic, mechanical, or other means, now known or
hereafter invented, including photocopying and recording, or in any information
storage or retrieval system, without permission in writing from the publishers.
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging in Publication Data
A catalogue record for this book has been requested
ISBN 0-203-36047-8 Master e-book ISBN
ISBN 0-203-37303-0 (Adobe eReader Format)
ISBN 0-415-15772-2 (hbk)
ISBN 0-415-15773-0 (pbk)
For Des Crawley, who defended this work, ad
utrumque paratus
Contents
List of figures and tables viii
Preface ix
1 Is male homosexuality adaptive? 1
Homosexuality, futile sex? 3
Orientation or preference? 5
How many gay men and just what is homosexuality anyway? 6
What do we know and what do we want to know about 7
homosexuality?
Explaining homosexuality? 8
Is evolution social? 14
Where to from here? 17
2 A biology of homosexuality 19
Homosexuality, a sexual inversion? 22
Does genetic inversion model homosexuality? 24
A chemical imbalance: the de-androgenised foetus theories 27
An anatomical difference? 39
Functional differences? 41
A genetic variation? 44
Discovering a difference: familial studies 45
A world of difference? Xq28 53
A typology of homosexuality 59
So where are we now? 62
3 Homosexuality as physical evolution 65
vi
Is homosexuality really adaptive? 65
Models of balance polymorphism: a balanced superior 76
heterozygotic fitness
Models of balance polymorphism: sperm competition 92
Models of balance polymorphism: density and frequency- 98
dependent selection
Models of balance polymorphism: frequency-dependent sexual 102
selection
Homosexuality as an evolutionary byproduct 115
Models of evolutionary futility: an overloving effect 117
Models of evolutionary futility: homosexuality—a continuously 120
occurring mutation?
4 Homosexuality as social evolution 125
Kin selection 128
Kin selection for a homosexuality gene 129
Kin selection for genes other than homosexuality 136
Kin selection and a social preference for homosexuality 140
Parental manipulation 145
A social adjustment 150
The central theoretical problem of sociobiology 156
5 The seven deadly sins of sociobiology 163
The first deadly sin: we are animals 164
The second deadly sin: explaining homosexuality is unnecessary 167
and misguided
The third deadly sin: trivial pursuits 170
The fourth deadly sin: a creeping reductionism 172
The fifth deadly sin: sly determinism 177
The sixth deadly sin: sociobiology is morally bankrupt 178
The seventh deadly sin: sociobiology is sexist 180
Conclusions 184
vii
Glossary 189
Bibliography 195
Author index 213
Subject index 219
Figures and Tables
FIGURES
2.1 Changes in LH in response to a single injection of Premarin 35
3.1 Types of natural selection 71
3.2 Proportion of 1881 generation in subsequent generation 86
3.3 Mean values for lowest acceptable intelligence and involvement 110
level
3.4 Double-matings, contraceptive use, and fertility 111
4.1 Population penetrance of direct versus indirect inclusive fitness 134
4.2 Reproductive success of bisexual and heterosexual women 152
TABLES
2.1 Maternal and paternal line gay relatives of homosexual men 55
3.1 Comparative content of fantasy material: frequency of 80
occurrence
3.2 Equilibrium in simulated selection experiment due to rare-male 100
advantage in Drosophila pseudoobscura
4.1 Reproductive success and descendants via kin selection and 133
direct reproduction
Preface
At the risk of entirely blowing my credibility at the outset, let me start this
speculative look at male homosexuality by saying that it is written by a
straight researcher who is less interested in explaining homosexuality, or in
passing comment on it as a lifestyle, than in the perspective of a theorist
confronted with an enormous difficulty threatening the tidy order of his
theoretical universe. Homosexuality is a major problem for those like myself
who believe that Darwinism is the great unifying force which social theory,
particularly psychology, so desperately needs for internal coherence.
Unfortunately, few would agree and there are many challenges to a
Darwinistic view of the social order. Perhaps one of the cleverest challenges
to confront evolutionary theory is homosexuality. Homosexuality seems to
be a tailor-made rebuttal of the great evolutionary credo—survival of the
fittest. How do we explain what is often a lifelong preference for non-
reproductive sex? Surely homosexuality defies evolutionary explanation?
This is a clever criticism. While far from being a life against nature,
homosexuality seems to contradict the Darwinian logic of individual
reproductive success. Yet any number of surveys tell us that there are many
homosexuals, and history attests to homosexuality’s antiquity. If
homosexuality is ‘futile’ sex, why are gay men still with us? Despite the
weight of a historical bad press, which sees homosexuality as a pathological
inversion of normal heterosexuality, its continuance suggests it is an
adaptive feature of evolution. What selective advantages might homosexuals
enjoy? How is such a widespread social behaviour to be explained? In this
book we set out to answer these and other questions from an evolutionary
perspective. While many would argue that Darwinism adds little to our
understanding of homosexuality, nevertheless, causation is an intriguing
puzzle and, if a diverse gay literature is any guide, is often a source of
confusion for homosexuals themselves. Apart from being a purely intellectual
puzzle, these questions also touch on much broader issues about the nature
of biosocial research.
If the genesis of a book arises from dissatisfaction, mine was professional.
Whatever the truth about homosexuality, as a social psychologist I came to
see that social constructivism, my profession’s dominant paradigm, had