Biological determinism of human gender roles

Biological determinism of human gender roles is the belief that human sexuality is controlled by an individual's genes or some component of their physiology. This is an aspect of biological determinism, the wider belief that human behaviour is determined by biological factors. Both beliefs ignore the contribution of learning and other environmental factors in a person's development.

Lynda Birke's In Pursuit of Difference argues that the discipline of human biology often presents "clear-cut differences" between sexes with regards to chromosomes, genetics, and inheritance. However, while obvious physical differences between males and females exist and develop during puberty, hormonal differences are "not absolute". There is a broad range of reproductive anatomy that doesn't necessarily fit the "gender definition" of male or female. According to the Intersex Society of North America, "a person may be born with mosaic genetics", differing in their chromosomal configuration.

Though scientists are unsure as to whether homosexuality can be attributed to biological or social factors, LGBT rights activists have used the theories of biological determinism to support their cause. This has become a frequent point of dissension between pro-gay individuals and anti-gay individuals. Because a single cause has not been determined as the cause of homosexuality, many scholars theorize that a combination of biological and social causes determine one's sexual orientation.Gay rights advocates believe that proving that homosexuality has a definite biological basis will prove it to be an unchangeable characteristic, thus allowing homosexuals to be protected under the Fourteenth Amendment in the United States. One area of research that has been a valuable tool for gay rights activists has been Dean Hamer's work studying the "gay gene". Another researcher who worked with Hamer in finding evidence for biological influence in male homosexuality was Simon LeVay, a neuroscientist. In 1991, LeVay published an article in Science that detailed the difference in hypothalamic structures between homosexual and heterosexual men. His findings in studying the INAH-3 implied that "sexual orientation has a biological substrate". Though his research showed that there was a biological basis in sexual orientation, LeVay cautioned against people interpreting his article to say that he found that homosexuality is genetic, emphasizing that he did not "locate a gay center in the brain—[as] INAH3 is less likely to be the sole gay nucleus of the brain than part of a chain of nuclei engaged in men and women's sexual behavior". He merely hoped that his work would serve as a catalyst in working towards finding more evidence that homosexuality is at least partly genetic.

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