GUEST OPINION: Homosexuality is biological, not just genetic
Peter Renn '06
Issue date: 3/18/04 Section: Opinion
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WHETHER HOMOSEXUALITY is innate, whether it can be changed, and whether it is immoral are three distinct questions that, for various psychological reasons, are often treated as one. And because many people - including policymakers and judges - will inevitably conflate them despite their logical independence, the question of what causes homosexuality remains relevant. Over the last decade, there has been an avalanche of evidence suggesting the existence of a biological substrate to sexual orientation.
First, it is difficult to dispute that genes play some role in the development of homosexuality. Recent studies using twin registries show that the concordance of homosexuality in identical twins is consistently higher than that between fraternal twins. This evidence, combined with molecular genetic studies and research showing that homosexuality runs in families, suggest that genes exert at least some influence on some forms of homosexuality.
But the media's focus on genes has obscured the dominant biological theory of homosexuality - a theory that doesn't directly rely on the genetic evidence. Let's begin with a simple observation: most men are attracted to women and most women are attracted to men. Whatever causes this sex difference is also likely to bear on why a non-negligible portion of the population deviates from it. According to the dominant biological theory, this difference in who we're attracted to is caused by a corresponding difference in the regions of the brain that control sexual attraction. The blueprint for how this region develops is prenatally determined in the womb by hormones, whose upstream cause is not wholly dependent upon genes. Thus, differences in exposure to prenatal hormones cause differences in sexual attraction. Supporting evidence comes from numerous studies demonstrating differences between gay men and lesbians and their heterosexual counterparts on a laundry list of traits linked to prenatal hormones (e.g. specific cognitive abilities, certain brain structures, and auditory systems).
First, it is difficult to dispute that genes play some role in the development of homosexuality. Recent studies using twin registries show that the concordance of homosexuality in identical twins is consistently higher than that between fraternal twins. This evidence, combined with molecular genetic studies and research showing that homosexuality runs in families, suggest that genes exert at least some influence on some forms of homosexuality.
But the media's focus on genes has obscured the dominant biological theory of homosexuality - a theory that doesn't directly rely on the genetic evidence. Let's begin with a simple observation: most men are attracted to women and most women are attracted to men. Whatever causes this sex difference is also likely to bear on why a non-negligible portion of the population deviates from it. According to the dominant biological theory, this difference in who we're attracted to is caused by a corresponding difference in the regions of the brain that control sexual attraction. The blueprint for how this region develops is prenatally determined in the womb by hormones, whose upstream cause is not wholly dependent upon genes. Thus, differences in exposure to prenatal hormones cause differences in sexual attraction. Supporting evidence comes from numerous studies demonstrating differences between gay men and lesbians and their heterosexual counterparts on a laundry list of traits linked to prenatal hormones (e.g. specific cognitive abilities, certain brain structures, and auditory systems).