Do you think we will ever know what causes Homosexuality

[Angrboda]

It's true we don't know what causes sexual dimorphism and related phenomenon associated with it, but we have some good theories about the split between homosexuality and heterosexuality. Heterosexuality is favored and retained because it has a high propensity to result in procreation. Homosexuality is theorized to be a result of desirable epigenetic effects being transmitted such that heterosexual individuals pass on the trait because it benefits them to have those genes, and homosexuals simply inherit the epigenetic factors that were preserved by their heterosexual ancestors. As to the proximal cause, what specific formal causes result in the expression of a homosexual sexual orientation, a lot of that is unknown, but the general outlook appears indisputable. Like most traits, certain combinations of genetic, epigenetic, and environmental or developmental factors combine to result in the orientation. For example, there has been some work that suggests certain structural aspects of the brain are different in homosexuals and heterosexuals. Also, it is known that, the later in the birth order the child is, the more likely the child will develop a homosexual orientation. For male children, the theorized mechanism is that during pregnancy with a male child, the woman's body sees the high levels of male hormones in the blood as a result of the developing fetus as an immunological threat, and responds by developing ways to mute the male hormones. Therefore, the more male pregnancies a woman has, the better her body becomes at suppressing male hormones, resulting in a less "male friendly" blood environment for later male fetuses, causing unexpected feminization. There are likely other causes, but this hypothesis shows how the complicated interplay of genes and environment can result in unexpected developmental results, including specific sexual orientations. (Chuck's point becomes very salient when we ask what is the formal cause of heterosexual orientations? We have some ideas as to why the trait is preserved, but not how the trait works, instrumentally, nor what specific developmental factors result in its expression.)