In my recent study of the Amygdala, a brain structure that accounts for much of the in-fighting in couples, I found something possibly more interesting. Brain scans of this region have found that gay males have similar patterns as hetero females, and vice versa, gay females exhibit a patterns similar to hetero males.
This is interesting because it not only provides genetic evidence for human sexual orientation (both homosexual and heterosexual), but also provides a new avenue of study. Indeed, it is possible that sexual orientation develops before sexual organs do.
Here is the excerpt from Wikipedia:
Recent studies have suggested possible correlations between brain structure, including differences in hemispheric ratios and connection patterns in the amygdala, and sexual orientation. Homosexual men tend to exhibit more female-like patterns in the amygdala than do heterosexual males, just as homosexual females tend to show more male-like patterns in the amygdala than do heterosexual women.
It is evident in humans that gender identity is programmed during fetal and neonatal development; however an individual’s sexual orientation development in these early stages has not yet been determined. It was observed that amygdala connections were more widespread from the left amygdala in homosexual males, as is also found in heterosexual females. Amygdala connections were more widespread from the right amygdala in homosexual females, as in heterosexual males.
The source material from the National Academy of the Sciences, Sexual orientation and its basis in brain structure and function.