Female Choice Or Male Sex Drive? Researchers Investigate Animal Courtship Behavior

The erotic and rather flamboyant displays of male animals are explained in Charles Darwin's theory of "female choice" as a male's way of wooing the ladies and proving they are better than other competing mates. A new study from McMaster University, however, challenges this long-held belief, suggesting females don't actually have a mate preference and that males have to come up with another excuse to dance, sing and shake their tail feathers.

"Darwin's female choice theory has become the foundation for explaining the presence of exaggerated secondary sexual traits in many males, such as the peacock's tail feathers," Rama Singh, one of the study authors and an evolutionary biologist, explained in the university's news release.

"It has also led to a cottage industry based on the idea that female choice is based on the genetic quality of the males, known as the 'good gene hypothesis'," Singh added. "Sexually exaggerated traits are said to be male advertisements to females of their good genes, when in fact they may simply be a means of making the male more visible to females or intimidating other males."

So, did Darwin get it wrong? Do females "choose" larger males over smaller individuals based on coercion or preference?

McMaster Researchers seek to answer these questions in their latest study. Using a common variety of fruit flies, Drosophila Melanogaster, scientists sexually aroused a female with either a large or small male. Researchers then removed the male and offered the female two fresh males -- one small and one large.

The results of their findings would surely shock Darwin: Researchers concluded aroused females did not show any particular preference for large males and mated fairly randomly. This suggests that, once sexually aroused, females have no preference in terms of mates.

Furthermore, the lag time between mating displays and a female's acceptance to mate is often misinterpreted as females exercising mate choice. Instead, researchers explained this lag time could be attributed to the amount of time it takes female fruit flies reach a state of arousal.

"In matters of mate choice and mating, there is no such thing as pure male charm," Singh said in the release. "All male moves can be seen as tinged with direct or indirect coercion or threat of physical force."

That's why researchers proposed the term "male sex drive" be used as a complement to Darwin's "female choice."

"In the case of humans," Singh added in the release, "things are different. Sexual behaviors are not hard wired; we assume that they can be modulated and moderated through rules of social interactions imposed by the brain's veto power over the body."

Their study was recently published in the journal PLOS One.

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