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The Politics of Finding Homosexuality Genetic

The Politics of Finding Homosexuality Genetic
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January 7, 1992, Section A, Page 14Buy Reprints
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To the Editor:

"Are Some People Born Gay?" (Op-Ed, Dec. 17) by Michael Bailey and Richard Pillard presents the reader with an example of a disturbing trend in which investigators make stronger sociobiological claims in the popular press than are warranted by the data they present in scientific journals. Here the authors state, "Science is rapidly converging on the conclusion that sexual orientation is innate." In support they cite their study of male twins.

But the results of the authors' study are unclear. It showed that an identical twin was much more likely to be gay (52 percent in this case) if his twin was, than a nonidentical twin (22 percent) or the adopted brother (11 percent) of a gay man. This supports a genetic theory only if one accepts the premise, buried deep in the original article, which appeared in Archives of General Psychiatry, that "because all types of relatives studied . . . were reared together they are all perfectly correlated for shared environment." This assumption is dubious.

As most people know, the same set of parents often treat siblings in dramatically different ways. If this was the case for the siblings under study, they could not have been perfectly correlated for shared environment, because parental treatment, it may be argued, is the most important aspect of a child's environment. If one makes the plausible assumption that identical twins are more likely to be treated similarly and interact more intimately than nonidentical twins or a boy and his adopted brother, the study can be reinterpreted as supporting an environmental basis for male homosexuality.

Furthermore, the authors omit from the Op-Ed article interesting evidence against their conclusion that appeared in their own scientific paper. They found that the biological nontwin brothers of gay men were only about as likely to be gay (9.2 percent) as were the adopted brothers of these men (11 percent). One would expect a significantly higher concordance among nontwin biological brothers if genetics played a strong role in sexual orientation.

A final point is especially pertinent. The authors cite Simon LeVay's controversial work showing brain differences between homosexual and heterosexual men as support for their position that sexual orientation is innate. If confirmed, this work would only demonstrate what has long been known -- disparate human behaviors are mediated by disparate brain structure and chemistry. Mr. LeVay's work does not indicate whether these differences arise from innate or environmental causes.

Much recent neurobiological research has shown that mammalian central nervous system structure and biochemistry are highly responsive to early environmental stimuli and retain a degree of plasticity in later life. It is notable that if one agrees with the results of both Mr. Le Vay's and the Bailey-Pillard study, one is forced to conclude that the structures Mr. Le Vay correlates with male homosexuality could not be determined solely by genes or prenatal endocrine influences, because about half the people who shared these innate factors display different orientations and, correspondingly, different hypothalmic structures.

The political stakes are high in this research, and they reach far beyond the issue of male homosexuality. The more our proclivities are thought to be genetic, the more we neglect life histories and the less is our interest in attempting to change others through the environment.

In times of budget cuts this perspective can lead to reduction of funds for psychotherapy, services for children and other critical psychosocial interventions. SETH MANOACH New York, Dec. 17, 1991 The writer is a student at Cornell University Medical College.

A version of this article appears in print on  , Section A, Page 14 of the National edition with the headline: The Politics of Finding Homosexuality Genetic. Order Reprints | Today’s Paper | Subscribe

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