Essentialism vs. social constructionism in the study of human sexuality - The Use of Theory in Research and Scholarship on Sexuality

Journal of Sex Research,  Feb, 1998  by John D. DeLamater,  Janet Shibley Hyde

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These studies seem to provide evidence of a genetic influence on sexual orientation in both men and women. They do not, however, provide evidence of complete genetic determination, which would require a concordance rate of 100% for identical twins.

Moving to the micro level of analysis, Dean Hamer and his colleagues reported that they have identified a particular gene on the X chromosome, named Xq28, that explains some cases of male homosexuality (Hamer, Hu, Magnuson, Hu, & Pattatucci, 1993). Transmission is therefore from mothers to sons, and there is an increased incidence of homosexual orientation in maternal uncles, but not in fathers or paternal relatives. This research is controversial, in part because of failures to replicate the findings (Marshall, 1995), but nonetheless intriguing.

Brain factors. Another hypothesis has been that there are neuroanatomical differences between the brains of gays and straights. Often the attempt has been to link these differences to male-female brain differences. Much research has focused 6n the hypothalamus and two clusters of cells (nuclei) in it: the sexually dimorphic nucleus (SDN) and the interstitial nuclei of the anterior hypothalamus (INAH-1, INAH-2, and INAH-3) (Swaab, Gooren, & Hofman, 1995). Much of this research has been conducted with animals, and one might question the relevance to humans.

Perhaps the best known study investigating the hypothesis of hypothalamic differences in humans is LeVay's (1991) research. He found that INAH3 was larger in heterosexual women than heterosexual men and that INAH3 in homosexual men was similar in size to that of heterosexual women (no lesbians were included in the study). The study can be criticized on a number of grounds: (a) The sample size was very small; only 19 gay men, 16 straight men, and 6 straight women were included. (b) All gay men in the sample, but only six straight men and one straight woman, had died of AIDS. (c) The gay men were known to have been gay based on records at the time of death; the others, however, were just "presumed" to be heterosexual. Therefore, this study cannot be regarded as conclusive.

Hormones. For decades researchers have speculated that some kind of hormone imbalance was responsible for homosexuality. Perhaps, the reasoning went, gay men are low on testosterone and lesbians are low on estrogen or perhaps high on testosterone. Recent studies fail to show any differences in testosterone levels between male homosexuals and male heterosexuals (Banks & Gartrell, 1995; Gooren, Fliers, & Courtney, 1990). Fewer studies of hormonal differences between lesbians and heterosexual women have been conducted. These studies showed no differences between the two groups in testosterone levels (Banks & Gartrell, 1995; Dancey, 1990; Downey, Ehrhardt, Schiffman, Dyrenfurth, & Becker, 1987).

There has also been speculation that there might be differences between heterosexuals and homosexuals in other hormones such as the gonadotropins FSH and LH. Five of seven studies on LH levels in gay men compared with straight men showed no differences, and two showed higher LH levels in gay men (Banks & Gartrell, 1995), so there is not strong support for differences in LH levels.