Sexual Selection?

A recent peer-reviewed study (Bailey, et al.) calls into question the universality of sexual selection. The University of California research team noted the following: “The variety and ubiquity of same-sex sexual behaviour in animals is impressive — many thousands of instances of same-sex courtship, pair bonding and copulation have been observed in a wide range of species, including mammals, birds, reptiles, amphibians, insects, molluscs and nematodes.”

The fact homosexuality has the power to alter the DNA and social structure of certain species – i.e. dolphins, bonobos, penguins, snails, and fruit flies – suggests an alternative selective force at work. For instance, among bottlenose dolphins, about half of male sexual encounters are with other males. In addition, according to the Times Online summary, “Almost a third of chick-raising pairs of Laysan albatrosses were found to be all female in one Hawaiian colony.”

What would be the evolutionary advantage of such a force? In the case of the Laysan albatross, female-female pairings have more advantages than single females, suggesting a hierarchy of selective forces. Another prominent theory suggests that homosexual pairings constitute an alternative, cooperative child-rearing strategy. Dr. Joan Roughgarden, a professor at Stanford University, subscribes to this theory and views mating in terms of “game theory” and the set of trade-offs that will ensure the greatest chance of offspring survival. The authors of the study also propose that homosexuality can result from mistaken identity and group bonding.

In light of these findings, does sexual selection need to be revamped? Should it be replaced by the Rougharden model of social selection? Or can we acknowledge a spectrum of selective forces? I personally think that these studies tend to dramatize Darwin’s faults; we know that sexual selection is at work in nature, whether or not it’s the only or predominant force is up for debate. However, I do not believe these findings constitute a paradigm shift as such.

For the article in Times Online, go here.
For the full study, go here.

-Alyssa Martin