Sexual orientation – in the genes?
Is homosexuality a lifestyle choice or an innate biological disposition? The idea that it is a choice is certainly widespread – a part of several mainstream religious doctrines and political ideologies – and is used to condone significant discrimination against homosexuals and the criminalization of homosexual behaviour. But what does the science say? The broad conclusions are that sexual orientation is an innate disposition – no different from whether you are left or right-handed – that it is affected by genetic influences and that it reflects differences in brain structure and function. I will consider the evidence of genetic effects on sexual orientation here, including some recent additions – a later blog will look at the neurobiological findings. A number of family and twin studies of the heritability of sexual orientation, starting in the 1950’s, found significant genetic influences: the statistical likelihood of an individual being homosexual increased somewhat if t