

How the human penis lost its spines - tokenadult
http://www.cnn.com/2011/HEALTH/03/09/penis.spines.genes/

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btilly
The article talks about the genetics, but doesn't really answer the
evolutionary question. So I'm going to speculate in a somewhat informed
fashion.

First I'll start with a fun fact. Humans have a penis that is several times
larger than you would expect looking at other primate species. In fact there
is clear evidence that humans have undergone sexual selection for penises that
women like. (And there is evidence that women enjoy size.) By contrast what a
chimp's penis is like is pretty much the least important thing about him as
far as the female is concerned. Much, much more important is how big and
strong he is, and likely to pound her if she doesn't comply with his wishes
RIGHT NOW. (Chimp sexual behavior is really not very nice.)

Therefore I'm going to propose a hypothesis. They have suggested that spines
help in removing your competitor's sperm. I'm going to suggest that spines are
less pleasant for females. Therefore in humans, who seem to have undergone
sexual selection based on what women think about men's penises, spines have
been lost. While in most other species, where female preference on penises is
not a sexual selection criteria, spines win.

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joshu
It's always the last place you look.

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jarin
Well, I'm glad we got that cleared up.

