> There are a number of evolutionary puzzles about human sexuality.
> Concealed ovulation is one, which Jared Diamond discusses in The
> Third Chimpanzee.  Another is the fact that the human penis is
> considerably larger than that of other primates.  There is no
> obvious reason why that should be so.  The location of the
> clitoris is such that most women do not achieve orgasm as a
> result of penetration.  This is a bit puzzling, too.  Menopause,
> another human idiosyncrasy, remains unexplained.
>

Let me take a speculative crack at these.

Menopause is reasonable given the huge physical difficulties bearing
children once we gained big brains and big heads. Women that maintained
reproductive ability would have died from childbirth and natural selection
would disfavor them.

Penis size might have served the sexual selection role of, say, peacock
feathers and other "wasteful" resource deployments found in many male
species.

Paleo food tie-in: does paleo eating increase sex drive? Does eating more
meat make you more interested in sex?

--Richard