Is there a Gay Gene? Does it Matter?

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Is there a Gay Gene? Does it Matter?

by Doug Futuyma

‘Science for the People’ Vol. 12, No. 1, January/February 1980, p. 10–15

Doug Futuyma teaches in the Department of Ecology and Evolution at the State University of New York at Stony Brook, and does research on the genetics and ecology of insects. His book Evolutionary Biology was published recently by Sinauer Associates (Sunderland. M A). Doug and his mate, Bruce Smith, live in Stony Brook. 

As most readers of Science for the People are aware, speculations about the evolutionary and genetic bases of human behavior have stirred controversy since the publication of E.O. Wilson’s Sociobiology: The New Synthesis in 1975.1 In the early stages of the debate, Wilson2 claimed innocence of any concern with the political and social implications of sociobiological theory: but in On Human Nature3, he acknowledges these implications by explicit discussion of social issues. Much sociobiological speculation, in On Human Nature and elsewhere4, seems ready made for the forces of oppression: apparently little more than Social Darwinism clad in new jargon, it seems to rationalize sexism, xenophobia (including racism), and capitalism, whether its authors intend such rationalizations or not. Indeed, Wilson denies any such intention in On Human Nature, and goes further: he clearly is proud to present sociobiological hypotheses that purport to affirm human rights and egalitarianism. 

Foremost among these hypotheses is his argument, drawing on J.D. Weinrich’s work5 for supportive data, that homosexual behavior is not necessarily the pathological, abnormal perversion of nature that the Judaeo-Christian tradition and most of Western society portray it to be: rather, Wilson suggests, there is “a strong possibility that homosexuality is normal in a biological sense, that it is a distinctive, beneficent behavior that evolved as an important element of early human social organization. Homosexuals may be the genetic carriers of some of mankind’s rare altruistic impulses.” Thus “the traditional Judaeo-Christian view of homosexual behavior is inadequate and probably wrong,” and “it would be tragic to continue to discriminate against homosexuals on the basis of religious dogma supported by the unlikely assumption that they are biologically unnatural.”6 

As a gay person, I can only applaud Wilson’s humanitarian concern: I agree that discrimination against gays is tragic. I consider the traditional Judaeo-Christian view of homosexuality to be barbaric, and I consider the oppression of gays, in Christian and non-Christian societies alike, an evil that demands moral outrage. However, I find Wilson’s argument scientifically unsatisfying and politically dangerous: and precisely because this is one of the rare sociobiological arguments that arrives at an appealing libertarian conclusion, I would like to analyze it with the confidence that I will not be accused of fearing the awful truths that sociobiology threatens to reveal. 

Theories of Sexual Orientation 

An enormous part of the literature on sexual orientation is concerned with the “etiology,” or causes, of homosexuality — motivated by the desire to “cure” homosexuals or to prevent the development of a homophilic orientation.7 Moreover, the theories are mostly designed to account for the origin of homosexuality, rather than for variation in sexual orientation — a fine but critical distinction, for as Hoffman8 says, those who inquire about the origins of homosexuality but not of heterosexuality assume without evidence that heterosexuality “naturally occurs,” so that its origins need not be probed. Many psychodynamic theories are of this kind: they assume that homophilia is abnormal or pathological, and usually pronounce a value judgement on it as well, often by appeal to evolution. Thus the psychiatrist W.J. Gadpaille considers homosexuality to be “pathognomonic of disordered sexual development. The view of cultural relativity seems to be without justification… Biological intent… is to differentiate male and female both physiologically and psychologically in such a manner as to assure species survival, which can only be served through heterosexual union.”9 This clearly is a reflection of the attitude that Wilson hopes to combat. 

Theorists who hold that homosexuality is pathological have variously argued that it has psychodynamic causes, such as disordered relations with parents (e.g., close-binding mother. absent father); that hereditary or environmental levels of sex hormones play a role; or that genetic differences among people predispose them to either a heterosexual or homosexual orientation. Any of these theories may equally well be propounded by those who do not make moral judgements. Kinsey et al.10, Ford and Beach11, and C. A. Tripp12 have argued that sexual orientation develops, as do many other traits of personality, in response to a sequence of positive and negative reinforcing stimuli during development. And Wilson is not the first to suppose that differences in sexual orientation are the consequence of different, adaptive genotypes.13 

The Sociobiological Theory of Homosexuality 

By assuming that homosexual behavior is an evolved trait, which therefore must have some genetic basis. Wilson must confront the problem: How could homosexuality evolve if homosexuals, by not reproducing as much as heterosexuals (presumably), tend not to propagate the very genes that predispose them to homosexual behavior? The answer that emerges from sociobiological theory is very simple. Genes predisposing an individual to homosexuality may be carried, even if not expressed. by the relatives of homosexuals (because related individuals, of course, inherit many of the same genes from their common ancestors). Thus if homosexuals, freed from preoccupation with their own children, helped to raise their nieces or nephews, the genes for homosexuality carried by these relatives would survive and be propagated. Such genes could actually be advantageous, in the sense that they would improve the chances for survival of related individuals who carry copies of those same genes. This is one of many applications of the theory of “kin selection,” which can explain the evolution of many traits, such as altruistic behavior, that seem socially beneficial. yet detrimental to the individual that displays the trait. In fact, Wilson ventures that homosexuals’ solicitude for relatives might be extended into a genetically programmed tendency to be exceptionally altruistic in general. 

By this argument from “kin selection,” one could predict either that (1) homosexuals and heterosexuals carry different genes, on average, predisposing them to their respective sexual orientations; or (2) heterosexuals and homosexuals might all have the same genotype, but a genotype that specifically programs one to develop into the heterosexual or the homosexual mode depending on which would be the most adaptive — just as a tree may develop thin flexible leaves in the shade, but thick, drought-resistant leaves if it develops in a drier, more exposed site. The first thesis, favored by Wilson14, may be called the hypothesis of genetic polymorphism (polymorphism is the existence of two or more genotypes within a population). The second, entertained by Weinrich15, may be called the developmental switch hypothesis. It resembles the idea of Kinsey — that we develop sexual orientation in response to our early environment — except that the developmental switch postulates that homosexuality and heterosexuality are specific, adaptive responses to certain environmental or social conditions. 

The Genetic Polymorphism Hypothesis 

Are humans genetically polymorphic for sexual orientation? Do gay people have different genes from straights? There is a large early literature that supposed so, some of which is almost laughably naive. For example, T. Lang believed that male homosexuals might really be genetic females (with two X chromosomes rather than an X and a Y) in male bodies, and claimed that the sex ratio among the siblings of German male homosexuals was shifted toward a preponderance of males, as if some of the genetic females in these families had been transformed into apparently male homosexuals.16 (This study isn’t quite as amusing when one reads that Lang obtained his list of homosexuals from secret police lists in the 1930’s.) 

There is a confused, contradictory literature on whether or not homosexuals differ hormonally from heterosexuals. Whether they do or not, a hormonal difference would not imply a genetic difference in any case, since hormone levels are affected by a multitude of physiological and environmental factors. The only acceptable evidence that differences in sexual orientation might be genetically based would have to come from the study of relatives — from evidence of transmission within families. But in humans, relatives (e.g., siblings) share not only genes, but a panoply of common environmental factors: parental attitudes, learning experiences, playmates (including each other), and so forth. That is, children inherit not only their parents’ genes, but their attitudes, values, religious beliefs, and so on. To demonstrate a genetic basis for behavior, it is necessary to separate the potential genetic component of this inheritance from the non-genetic component. This is why the studies of separately reared twins and of adopted children have been the only source of data that are even momentarily worth considering in the controversy over the inheritance of IQ.17 

In the case of sexual orientation, no such data exist. There are no studies of the degree of concordance of sexual orientation of separately reared twins or other relatives: indeed, there are only two studies of sexual orientation in twins. The one by Heston and Shields18 that Wilson quotes in his support includes a sample size that is simply too small to demonstrate anything at all. The only extensive study is by F. J. Kallmann19, who devoted his life to proving that psychological traits are genetically based.20 Kallman made the astonishing claim that the cotwins of 40 monozygotic (i.e., “identical”) homosexual twin “index cases” were homosexual in every single case. 

Kallman’s other major work, on schizophrenia, has been severely criticized: for example, he apparently concluded that schizophrenia is inherited by diagnosing schizophrenia from 25-year-old hospital records written before 1902, when the entire vocabulary of psychiatry was different.21 In the case of his study of homosexuals: 

  • He does not specify how he determined which twins were monozygotic (“identical”) and which were dizygotic (“fraternal”); and the methods usually used in his time are untrustworthy.22 He doesn’t even say whether he made this determination before or after he obtained the information on the cotwins’ sex histories. 
  • He claimed that many of his subjects were emotionally and socially maladjusted, a maladjustment which may well have been in the eye of the biased heterosexual beholder, but which nevertheless raises doubts as to whether or not the sample was representative, or whether the homosexual behavior may have been a pathological manifestation of a psychological disorder.
  • Despite his assertion that sexual orientation is very highly (indeed, incredibly) heritable, he found no exceptionally high incidence of homosexuality among the dizygotic male cotwins or the fathers of his index cases. 
  • For only 8 of 71 male homosexual index cases was he unable to obtain “a complete investigation of… sex history.” Anyone who is familiar with the protective reactions adopted by homosexuals against social oppression will find his or her credibility severely taxed by the claim that virtually every one of a group of homosexual cotwins chosen a priori would not only acknowledge homosexuality, but volunteer enough information to conclude that they “tend to be very similar in the part taken in their individual sex activities” (emphasis in the original).23 
  • And in any case, there is no evidence that the twins were reared apart, so no genetic conclusions can be drawn from the study. Thus there is no evidence for a genetic basis for variation in sexual orientation. 

The Developmental Switch Hypothesis 

The other possible version of the kin-selection argument is that gay people, rather than having special genes for homosexuality, have the same genes as heterosexuals — but genes which specifically program either homosexuality or heterosexuality, depending on which would be adaptive for the individual. For example, Weinrich has suggested that it might be appropriate to become homosexual if one’s physical condition precluded the likelihood of becoming a successful parent.24 This idea is quite similar to the “learning” theory of Kinsey et al., which holds that sexual orientation, like our tendency to become extroverted or introverted, peaceful or belligerent, analytical or fanciful, arises through a long succession of conscious or unconscious responses to innumerable experiences or stimuli. The difference is that the evolutionary notion of an adaptive “developmental switch” is a biological determinist view — we are genetically programmed for specific responses to specific situations — whereas the “learning” theory is as free of determinism as a psychological theory of personality development can be. 

The subtle distinction between these theories can be illustrated by a rather absurd analogy. Why do some people speak with New England accents and others with Georgian accents? A “learning” theory would hold that as children we develop our particular speech patterns by responding to a succession of stimuli – the sounds we hear and imitate. A “biological determinist” theory might suppose that our environment triggers a physiological change, perhaps in the vocal cords, so that we develop either broad a‘s or a slow drawl, depending on whether our childhood winters were cold or warm. The one theory emphasizes the action of environmental events on an initially “clean slate”; the other invokes specific genetically controlled alterations in the developing person, that then affect the responses to environmental events. 

But although the two ideas are philosophically different, it is hard to know how to distinguish them in practice. By analogy, we may agree that each of us has, or at least had when younger, the genetic capacity to develop fluency in both English and German — but shall we take the biological determinist position (more extreme than the most rabid sociobiologist would take) that our genotype programs us to form perfect umlauts when we develop in a German environment, and not to do so in an English-speaking culture? Or shall we simply say that our genotype allows us the flexibility to develop the capacity for umlauts or not? 

If Wilson cannot offer a way of telling whether our genotype programs or simply permits various paths of development, his determinist theory is untestable, and so is bad science — or isn’t scientific at all, some philosophers would say.25 The only tests of the theory that Wilson offers are actually very weak. Biological determinists are fond of pointing out similarities between human behavior and that of other mammals as evidence of the evolutionary, hence biological, foundations of human behavior. And Wilson indeed notes that homosexual behavior has been observed in many species, especially of primates. But every evolutionary biologist is aware that the similarities between very different species may not be homologous, with the same genetic foundation, but analogous, like the fish-like form of fishes and porpoises. Indeed, Frank Beach26, a leading student of comparative sexual behavior, has stressed that there is no reason to suppose that homosexual behavior in other animals is homologous to that in humans, and notes that they are actually very different in some crucial respects. 

Wilson’s other line of defense is to argue that if homosexuality is genetically programmed because of its kin-selected advantage, we would expect homosexuals to play special, people-oriented, social roles. I’m not quite sure of how he logically arrives at this conclusion, but in any case he cites as evidence cases of homosexual or transvestite men playing the role of shaman or berdache in some pre-industrial cultures, and the supposed tendency of homosexuals to enter upwardly mobile, white collar professions in western industrial societies. The evidence that either of these claims is true is far from compelling (because, for example, homosexuals may simply “come out” more often if they are in these professions); and I fear that by citing this “evidence” Wilson may contribute to the propagation of stereotyped myths about how different gay people are from heterosexuals. But there is strong reason to believe that if gays tend to enter special professions in our society, they do so in response to social pressures that make some professions safer than others. In other words, these roles are imposed, not prompted by a biological imperative. And it is certainly possible that social imposition was as important in pre-industrial cultures as in our own. The evidence that homosexuality is a genetically programmed adaptive developmental pathway is absurdly weak. 

Does it Matter? 

Wilson’s argument that homosexuality is biologically “natural” — and the more general argument that it is “genetic” or “inborn” — appeals to a great many gay people. (The relevant excerpt from Wilson’s book, and an enthusiastic review, appeared in a major gay periodical, The Advocate27.) It is an appealing argument for at least two reasons: the answer it provides to heterosexual bigots who claim that homosexuality is an “unnatural” “crime against nature”; and the secret satisfaction it gives to inwardly guilty homosexuals that their sexual orientation isn’t their fault, for it was programmed into them by a biological imperative which absolves them from responsibility. 

Insofar as any deterministic theory of the origin of homosexuality panders to “gay guilt,” it is, I feel, psychologically and politically counterproductive. Above all else, gay people need to cultivate self-acceptance, and to cleanse themselves of the notion that they need to blame their orientation on anyone or anything — for this implies that their orientation is a fault. 

Indeed, the entire focus on the causes of homosexuality is scientifically questionable and politically repressive. To concentrate on discerning the causes of homosexuality is, first, implicitly to judge it a personal or social problem, and to divert attention from the more pressing, liberating questions: What cure is there for society’s homophobic, oppressive attitudes? And how can we help people whose judgement of their own worth has been warped by repressive societal values? 

Moreover, the focus on the causes of homosexuality is flawed at its very base. The behavioral traits for which biological bases have been sought are most often the characteristics that are perceived as politically or socially threatening. There hasn’t been very much debate over the possible genetic basis of the ability to whistle, or of people’s variable appreciation of Beethoven, or, in the realm of sexual orientation, of the degree to which we are sexually and emotionally attracted to people on the basis of their hair color, intellectual depth, or other physical or personal characteristics. Attraction to people on the basis of their sex is singled out for analysis as a special, separate characteristic — it is reified — because it is viewed as a social problem, not because it is scientifically interesting to any unusual degree, or because it is a separable, independent part of the personality. Indeed, the greatest insult to gay people, and the greatest scientific error, may be to divorce “sexual orientation” from the emotional context of feelings and responses that an individual has toward other people a complex of responses in which the sex of other people enters as only one of many interdependent variables. We do not have simple knee-jerk responses to the single stimulus “male” or “female” — we have complex emotional, affectional, and erotic responses to the multitude of stimuli another individual presents; and it is folly to suppose that the response to the person’s sex is genetically or psychologically separable from the rest of us. 

Insofar as the sociobiological theory of homosexuality serves as an argument for gay rights and social acceptance, it is unfortunately a flawed and indeed dangerous argument. It is dangerous because it is certainly within the realm of possibility that tomorrow’s research could disprove the hypothesis that homosexuality has any biological foundation whatever — and where then lies the argument for gay rights? It is a flawed argument because it accepts and rests on the same profoundly non-sensical assumption that supports heterosexual bigotry: that “what is biologically natural is good; what is not, is bad” — the notion that our morals, ethics, and laws should be shaped to fit our biological urges, as we conceive them to be. To give Wilson credit, he remarks that “it would be… illogical, and unfortunate, to make past genetic adaptedness a necessary criterion for current acceptance”; but in the same breath he says that “it would be tragic to discriminate against homosexuals on the basis of religious dogma supported by the unlikely assumtion that they are biologically unnatural” — implying, as he does so often in his book, that biology should indeed inform ethics. 

The entire argument about sociobiology revolves about this crucial issue: that biology, natural selection. evolution cannot, by any logical deduction, serve as a guide for ethical progress. Thomas Henry Huxley, “Darwin’s bulldog,” made the point vigorously in 189328; critics of sociobiology have repeatedly made it today. Suppose the sociobiologists were right — that humans are innately aggressive, that men are genetically more prone to competitiveness than women, that homosexuality is the product of adaptive genes that confer a tendency to be solicitous and altruistic. In no way does it follow that we should promulgate armed conflict (or try to prevent it any more assiduously than if we believe that aggression is a product of culture): nor does it follow that we should discriminate against women in politics and business. Neither does it follow that homosexuals should be granted rights on the basis of their biology. Women, racial minorities, and gay people are entitled to freedom from discrimination not because of their biology, but because of our idealistic conception of the dignity of the individual. Whatever our biological evolution has been, our ethics are part of our cultural evolution, in which we have come to strive for humanitarianism and to combat oppression out of respect for human dignity

>> Back to Vol. 12, No. 1<<


  1. E.O. Wilson, Sociobiology: The New Synthesis (Harvard University Press, 1978). For early critiques see, e.g., Sociobiology Study Group, “Sociobiology — Another Biological Determinism,” in BioScience 26, 1978, pp.182-186 and Sociobiology Study Group, “Sociobiology — A New Biological Determinism,” in Ann Arbor Science for the People (eds.), Biology as a Social Weapon (Burgess, 1977), pp. 133-149.
  2. E.O. Wilson, “Academic Vigilantism and the Political Significance of Sociobiology,” in BioScience 26, 1976, pp.183-190.
  3. E.O. Wilson, On Human Nature (Harvard University Press, 1978).
  4. E.g., D.P. Barash, Sociobiology and Behavior (Elsevier, 1977).
  5. J.D. Weinrich, Human Reproductive Strategy: The Importance of Income Unpredictability, and the Evolution of Non-reproduction, Ph.D. dissertation (Harvard University, 1976).
  6. Wilson, 1978.
  7. S.F. Morin, “Heterosexual Bias in Psychological Research on Lesbianism and Male Homosexuality,” in American Psychology 32, 1977, pp.629-637.
  8. M. Hoffman, “Homosexuality,” in F.A. Beach (ed.), Human Sexuality in Four Perspectives (Johns Hopkins University Press, 1976), pp.164-189.
  9. W.J. Gadpaille, “Research into the Physiology of Maleness and Femaleness: Its Contributions to the Etiology and Psychodynamics of Homosexuality,” in Archives of General Psychiatry 26, 1972, pp.193- 197.
  10. A.W. Kinsey, W.B. Pomeroy and C.E. Martin, Sexual Behavior in the Human Male (Saunders, 1948).
  11. C.S. Ford and F.A. Beach, Patterns of Sexual Behavior (Harper and Row, 1951).
  12. C. A. Tripp, The Homosexual Matrix (McGraw-Hill, 1975).
  13. E.g. G.E. Hutchinson, “A Speculative Consideration of Certain Possible Forms of Sexual Selection in Man,” in American Naturalist 93, 1959, pp.81-91.
  14. Wilson, 1978
  15. J.D.Weinrich, 1976 and J.D. Weinrich, quoted in D. Stein. “Why Gays are Smarter than Straights: Homosexuality and Sociobiology,” in Christopher Street 3: 1, 1978. pp, 9-14.
  16. T. Lang, “Studies on the Genetic Determination of Homosexuality,” in Journal of Nervous and Mental Disease 92, 1940, pp. 55-64.
  17. R.C. Lewontin, “Genetic Aspects of Intelligence,” in Annual Review of Genetics 9, 1975, pp. 387-405.
  18. L.L. Heston and J. Shields, “Homosexuality in Twins: A Family Study and a Registry Study,” in Archives of General Psychiatry 18, 1968, pp. 149-160.
  19. F.J. Kallman, “Twin and Sibship Study of Overt Male Homosexuality,” in American Journal of Human Genetics 4, 1952; F.J. Kallman, “Comparative Twin Study on the Genetic Aspects of Male Homosexuality,” in Journal of Nervous and Mental Disease 115, 1952, pp.283-298; and F.J. Kallmann, Heredity in Health and Mental Disorder (Norton, 1953).
  20. Gadpaille, 1972 and N. Pastore, “The Genetics of Schizophrenia,” in Psychology Bulletin 46, 1949, pp.285-302.
  21. Pastore, 1949.
  22. I. Gregory, Fundamentals of Psychiatry (Saunders. 1968).
  23. Kallman, “Twin and Sibship Study,” 1952.
  24. Weinrich, 1976 and 1978.
  25. K. Popper, The Logic of Scientific Discovery (Harper and Row. 1968).
  26. F.A. Beach, “Cross-species Comparisons and the Human Heritage,” in F.A. Beach (ed.), Human Sexuality in Four Perspectives (Johns Hopkins University Press, 1976) pp. 296-316.
  27. The Advocate, 3 May 1979.
  28. T.H. Huxley, Evolution and Ethics (The Romanes Lecture, Oxford University, 1893).