Though homosexual behavior has been rewarded in over 1,000 organisms, it can be an evolutionary puzzle; since reproduction can't happen, there is a fitness cost, so why do it?
A new paper argues it's part of the ancestral condition in animals and that evolutionary biologists need to relax their traditional constraints on evolutionary theory. They also dispute the assumption that because different-sex behaviors are essential for sexual reproduction selection — or the tendency of beneficial traits that promote increases in population, size, or resilience — will eliminate sexual behaviors that do not immediately result in reproduction. On the contrary, they suggest that homosexuality is not always — and maybe even seldom — costly. They instead suggest that this behavior is what evolutionary biologists call “neutral,” meaning that it has neither negative nor positive effects and therefore persists because there’s no reason for natural selection to weed it out.
Scientists have found that male burying beetles engage in increased same-sex behavior when they perceive a higher cost of missed mating opportunities with females. This suggests that engaging with different-sex behaviors exclusively is actually disadvantageous because it reduces chances to display mating potential when mating opportunities are rare. That seems to defy the definition of mating, as people inside evolutionary biology might use it, but they won't want to be in your Twitter mentions so they are unlikely to correct anything in the paper.
For the article, they also use the terms “same-sex behaviors” and “different-sex behaviors” rather than homosexuality or heterosexuality to avoid conflation with terms for human sexual identities.
They also argue that scientific questioning into the persistence of same-sex sexual behaviors has long been observed through the lens of a human society that has historically judged some behaviors to be “normal” or “abnormal.” This tendency, they say, hindered understanding of animal behavior in that it has promoted research that only confirms pre-existing assumptions or even averts important steps in the scientific process.
