Epigenetics May Be a Critical Factor Contributing to Homosexuality, Study SuggestsThe artical linked to above makes very interesting reading. The existance of homosexual behaviour is counter-intuitive. It should die out as a trait because it is unlikly to foster successful reproduction; a perfect selection pressure for natural selection to work on. The article posites that homosexual behaviour is caused by a faulty transmission of epigenetic markers from a father to daughter or mother to son.
Here is the key paragraph from the article.
The study solves the evolutionary riddle of homosexuality, finding that "sexually antagonistic" epi-marks, which normally protect parents from natural variation in sex hormone levels during fetal development, sometimes carryover across generations and cause homosexuality in opposite-sex offspring. The mathematical modeling demonstrates that genes coding for these epi-marks can easily spread in the population because they always increase the fitness of the parent but only rarely escape erasure and reduce fitness in offspring.
Interesting?