I don't know where you heard that, how outdated it was, or if you mis-understood the materials, but that is PAINFULLY innacurate. There are no genetic markers that turn on/off based upon the order of birth. There CANNOT be any genetic markers in the child that do it, that much is basic biology. And any genetic switches in the mother shouldn't have an influence of the biology of a child.Originally Posted by UltimaLimit
I can't tell you WHAT causes homosexuality, no ethical scientist could. We have many theories (also known as guessing), but no facts support any particular theory well enough to know for certain. I've mentioned it before, but there are many cases of genetically identical twins with differing sexualities. So, presumably, DNA has nothing to do with sexual identity. Or, perhaps, no more than how some people are more genetically prone to some types of cancer than others.
Of course, admittedly, some psychological traumas CAN cause sexual disfuctions that mimic sexual identities. But there are relatively identifiable signs.