Is homosexuality genetic? Dr. Dean Hamer and his researchers at the National Cancer Institute claim that “male sexual orientation is genetically influenced.” Initially, they discovered elevated rates of maternally but not paternally related homosexuality in the families of 76 gays. This suggested potential maternal transmission of homosexuality through the X chromosome.
Thus, the team examined 22 regions, or “loci,” covering the X chromosome of 40 pairs of homosexual brothers who had volunteered to be studied through advertisements in homosexual publications. The researchers found that 33 of the 40 pairs of brothers shared identical genetic markers in five loci of the q28 region of the X chromosome. This led them to the conclusion that a gene or genes in this region influences the expression of homosexuality in at least 64 percent of the brothers tested. They interpreted this to mean that homosexuality is genetic after all.
What do other scientific authorities say?
Scientific authorities in the area are not convinced any connection has been established. For example, Ruth Hubbard, a professor emeritus of biology at Harvest University and coauthor of Exploding the Gene Myth, commented:
This study, like similar previous findings, is flawed. It is based on simplistic assumptions about sexuality and is hampered by the near impossibility of establishing links between genes and behaviour. Of the relatively small number of siblings in the survey, almost a quarter did not have [the appropriate] markers. Also, the researchers did not do the obvious control experiment or checking for the presence of these markers among heterosexual brothers of the gay men they studied.
In addition, an editorial in the prestigious British Medical Journal commented on the Hamer research as follows:
“The linkage results are ambiguous… In their original analysis, Hamer, et al. placed the homosexuality gene eight centimorgans distal to the most telomeric marker. The short physical distance between this marker and the telomere, however, renders this result questionable.”
The editorial concluded: “The claim of linkage of male homosexuality to chromosome Xq28 has wide social and political implications. Yet the scientific question is a complex one, and the interpretation of the results is hampered by methodological uncertainties. Further study is crucial to confirm or refute this finding.”
Finally, Dr. Paul Cameron and colleagues, after careful examination of this study and consultation with various experts, also rejected Hamer’s conclusions. They pointed out:
A correlation for specific genetic markers does not imply that a gene or genes caused the brothers’ homosexuality. The results could be pointing to another trait shared by these subjects and disproportionately common in gays, such as promiscuity, exhibitionism, or other personality characteristics known to be associated with male homosexuality.
Our other articles in this series can be found here: