More Evidence of Biological Basis of Sexuality

After the twin studies, evidence of differences in brain structure, as well as pointers to a genetic component to sexual orientation comes this study which presents evidence that sexual orientation is determined in part by conditions in utero. Taken in conjunction with earlier twin studies (that showed that when twins are fraternal (each with their own placenta), they have a slightly higher probability of being gay than siblings born individually, that identical twins (each with their own placenta) are much more likely to share the same sexuality, but that twins that share a placenta almost invariably share the same sexuality), the scientific evidence seems quite clear that sexuality is firmly established at birth. Here is an interesting synthesis of the major research that has been done on the biological origins of sexuality.