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Penis evolution: Is bigger really better?

April 08, 2013|By Monte Morin
  • An Australian study argues that female selection has driven the evolution of relatively large penis size in humans. (Boxes added.)
An Australian study argues that female selection has driven the evolution… (Proceedings of the National…)

Brace yourselves, gentlemen: Not only does size matter when it comes to penis length, but female preference for large genitalia is probably what drove the evolution of your manhood to begin with.

In a study published Monday in the journal Proceedings of the National Academy of Sciences, researchers concluded that penis length was just as important as height when it came to sexual attraction among women.

And just how did scientists figure that out?

They asked 100 Australian women to look at life-size, computer-generated images of men in the Full Monty and asked them to rate each one as a potential sexual partner. The virtual beaus were short, tall, fat, skinny and athletic, and had a variety of flaccid genitalia that stretched from 2 to 5 inches.

The relative attraction to penis length seemed to increase as the male images grew taller and more athletically built. It grew less important the shorter or more rotund the man was, however. Interestingly, the preference for larger male genitalia seemed to be stronger when the woman was heavier than expected for her height.

Not only did researchers consider each woman's answer, they considered how long it took her to deliver a verdict. A longer pause suggested the women were taking more time to admire a man's form, researchers said.

The findings, authors wrote, suggested that ancient women selected their mates, at least partially, on the basis of penis size.

"Before clothing, the nonretractable human penis would have been conspicuous to potential mates," wrote lead author Brian Mautz, an evolution and sexual preference researcher at Australian National University in Canberra. "Our results support the hypothesis that female mate choice could have driven the evolution of larger penises in humans."

The study contradicts a number of recent papers that conclude genital size is unimportant to most females. Mautz and his colleagues wrote that these studies relied mostly on direct questioning and are susceptible to bias and self-censorship.

In many other species, sexual organs have evolved in ways that improve fertilization after mating, and not prior to copulation. For example, the genitalia of some insects, like honey bees, explodes or breaks off inside the female to prevent other males from reproducing with her.

The human penis is also unique when compared to those of other primates, because of its large size. A gorilla's erection will measure, on average, 1 1/4 inches long -- about four times smaller than a human's.

Study authors were unable to say exactly why women were attracted to a larger penis.

"Some studies indicate that preference for a larger penis might arise because penis size is associated with higher rates of vaginal orgasm," the authors wrote.

"Regardless of the exact mechanism, however, our results show that female mate choice could have played a role in the evolution of the relatively large human penis."

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