All About The Penis, Men & Male Sexuality
The evolution of the penisHome Page
I need to say right now that we are talking more about the social evolution of human sexual behavior here than the physical evolution of the structure of the penis!
Sociobiologists argue that in our evolutionary history, male and female proto-humans were engaged in a mating game, a war of attrition, which led to different strategies evolving around reproduction: these roles were shaped by the biological investment each sex made in the sperm and egg, and the subsequent investment in the child.
Obviously this is much greater for a female than a male, because she has to carry the developing child for nine months.
This means that females would naturally look for a mate who was trustworthy and reliable, and likely to stay around for long enough to help raise the child. This was the way that a woman would ensure her reproductive success - the way she would most effectively spread her genes.
But for men, the pressure was different - a male had no especial investment in the child, except for an ejaculation. His best strategy therefore, would be to assert himself and breed as often as possible, possibly at the expense of other males lower down the social scale. His reproductive success would be ensured if he could fertilize as many females as possible.
Equally, of course, the survival of the child would be most likely if a female could attract the alpha male, the strongest, fittest, or best adapted to survive (assuming these characteristics were passed on to the child, or that the man stayed around to protect the female and child).
In the conditions in which we evolved as a species, therefore, there appear to have been two contrasting forces at work.
And the end result is that a man wishes to use his penis to inseminate
as many women as possible, so that through sheer reproductive force of
numbers, he leaves as many children as possible. A woman wishes to mate
selectively, with the best males, and keep them around after the birth.
A signal of strength, a kind of peacock's tail? (The peacock's tail is a sexual signal, for peahens are attracted by the largest and most colorful display. And while such displays do indeed tell the female something about the male's strength and fitness, a large penis doesn't really do that. At least, I don't think it does.....no, it's impossible! Still, we do rather admire a large penis. Oh, sorry, it's men who want a large penis, not women. I forgot.)
Second, therefore, the function of a large penis might just be that it was designed to impress other males - and perhaps put them off a sexual challenge. Could this, perhaps, explain men's obsession with penis size?
Certainly dominant male monkeys may use
their erections to intimidate other subordinate males - and while we
might like to think that this could hardly be human behavior, well, if
you have seen adolescent boys at work in the locker room, you know this
might actually not be so far from the truth.
But why would penis size be so correlated? It isn't, as we have already seen, correlated with body size (the gorilla is much bigger than a human). One theory is that the male with the longest penis and the largest volume of ejaculate was going to have the reproductive edge because he would shoot his load near the woman's cervix, and thus be more likely to fertilize her.
Bear in mind also that the reproductive edge would also be enhanced by a rapid ejaculation. This wasn't a time when sexual pleasure was especially important - this was about reproduction.
We can assume there was a distinct possibility that a man who was copulating was at risk both from predators and from other men, who might want to pull him off a woman as he was mating, and replace his semen with their own.
Men who made sex last for a long time might therefore be evolutionarily discriminated against and a rapid ejaculation might have become the norm. So - we have a (comparatively) large penis, and we ejaculate quickly.....the first trait might please women, the second tends not to.
But why are there men with small penises? How come they escaped this evolutionary lottery? That's a bit of a nonsensical question, because there are plenty of conditions which have been carried through the population even if they were evolutionarily disadvantageous.
(Mind you, even the idea that we ejaculate quickly is open to contention - gorillas ejaculate within a minute. Chimpanzees last all of seven seconds.
And you could argue that
women would wish to get sexual pleasure, so there would have been an
evolutionary pressure on men to actually last longer - otherwise,
how could the G spot have evolved? Generally this organ only gives a
woman a vaginal orgasm during intercourse after prolonged male
Randy Thornhill controversially claims that human males may have adapted to avoid the effects of female choosiness by using another strategy - rape. Thornhill calls this a genetic program, a way that nature has evolved of allowing all men a chance to reproduce.
Hmm.....social controls on rape would hold this in check, I suppose, but my main problem with the idea is that rape seems often to be about anger and power, and, I assume, is a conscious choice. I think that's pretty clear. And some rapists are already fathers. And most rape is violent. My other big problem is that Thornhill is an entomologist. (He studies insects.) I think we can dismiss this idea.
If this were true, then women are encouraged by generations of evolution to resist men
Other pages on the penis in the human psyche
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