I've long held a theory about homosexuality that a recent article lends credence to. I've examined homosexuality through a political-societal lens in this posting:
In this posting, I'd like to examine homosexuality through the lens of evolutionary biology. You see, those who condemn homosexuality do so by thumping on two texts, the bible and National Geographic. Bible thumpers thump and then leaf to Leviticus 18:22 which reads: "Thou shalt not lie with mankind, as with womankind; it is abomination." I invite such individuals to glance at Numbers 15:32-36 which states that those who profane the sabbath ought to be publicly stoned. However, at least in the case of bible thumpers I can concede that the text does condemn homosexuality.
In the case of those who open up their National Geographic and point to pictures of rutting and mating animals and say, "it's not nature's way", they've just got it wrong. It is Nature's way; they just lack an understanding of nature and specifically evolution. Homosexuality has existed in nature for eons, but the question, from an evolutionary standpoint is: "How?" Standard evolution deals with selective pressures which make certain individuals more successful than others in reproduction. As a result the genes that contributed to this success are passed on preferentially over less 'fit' genes.
Homosexuality poses a conundrum then to anyone who lacks another piece in the evolution puzzle: Kin Selection. It is possible to pass your genes on to the next generation without directly reproducing. You can accomplish this by helping your kin as much as possible. By helping your kin, who carry part of your genetic code, you can preferentially increase the survivability and reproductive success of your kin. This mechanism was proposed by W. D. Hamilton in the 1960's when explaining the evolution of altruism.
Since I am Canadian, I learned about the evolution of altruism using the example of our good old Canadian Beaver. When a beaver detects danger, such as a wolf, it slaps its tail loudly against the water to warn its peers of the impending danger. This behaviour attracts attention to itself, making it a target for predation. Thus, how did this behaviour evolve, considering that it lowers the reproductive success of the warning beaver? The answer is that the beaver's peers are relatives. Thus even if the beaver becomes the wolf's lunch, the beaver's genes can live on via the reproductive success of its relatives.
Arriving back at our original topic of consideration, how then can homosexuality have been allowed to survive the process of natural selection? I've long suspected that the notion of kin selection might be at work here too. I've long thought that if perhaps homosexual individuals helped in child rearing and caring, then their genes may have been passed indirectly through the offspring of the kin they assisted. Recently I chanced upon a study which proposes exactly this explanation:
This study of a Samoan homosexuals suggests that homosexuals do indeed assist in child rearing. It's important to note that similar studies have been conducted in the West but have failed to find such a correlation. It is proposed that the Samoan culture more closely replicates our ancient lifestyle and that the modern (western) biases and condemnation of homosexuality may be to blame for the failures of the western studies.
In conclusion, what is most striking, yet perhaps not blaringly obvious from this study is that opposition to homosexuality comes from those appealing to old sources such as the bible or appeals to nature's longstanding order. However, this study shows that, at least in evolutionary time scales, the bias against homosexuality is a modern invention.