Thursday, August 04, 2005

sperm competition

I must blog about this.

We examine some of the implications of the possibility that the human penis may have evolved to compete with sperm from other males by displacing rival semen from the cervical end of the vagina prior to ejaculation. The semen displacement hypothesis integrates considerable information about genital morphology and human reproductive behavior, and can be used to generate a number of interesting predictions.

Evolutionary Psychology 2: 12-23

Semen Displacement as a Sperm Competition Strategy in Humans

How interesting is that. Fascinating shit. We thought sperm competition only occured in invertebrates and less often in animals but, wow, in humans too.

Stumbled upon this while searching on sperm competition in spiders. Apparently I'm very outdated cos this article is dated Feb 2004. But heck, I'm still amazed as hell.

Even more amazing, is that a new study actually suggests that looking at pornography actually makes sperm stronger (what a pleasant excuse, eh?)

Looking at pornographic images of men and women together can increase the quality of a man's sperm, a new study suggests.

Pornography involving a woman alone or multiple women doesn't have the same effect.

Evolutionary biologist Professor Leigh Simmons of the University of Western Australia says the effect is based on an evolutionary process observed in animals known as sperm competition.

This occurs when semen quality increases according to the perceived risk of another male fertilising a female.

"Males ejaculate more sperm, or sperm of better quality, when the risk of sperm competition [the probability that a female will mate with more than one male] is high," Simmons writes in the journal Biology Letters today.

Simmons says his research now shows that just looking at an image of another man in action is enough to register as a case of sperm competition, causing a compensatory adjustment in the viewer's semen.

"Our data show that image content can have an impact on men's semen quality," he says.

"We show that ... human males viewing images depicting sperm competition had a higher percentage of motile [efficiently moving] sperm in their ejaculates."

More here.

Amaze-meh baybeh!

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