Why Men Don't Have Sensory Whiskers and Spiny Genitals

sciencehabit writes "Most male mammals wield a penis covered with spines made of keratin, the same material that forms fingernails, to sweep out competitors' sperm and irritate a female into ovulating. Even chimpanzees, our closest relatives, have penile spines. So why don't men? A new study suggests that this feature disappeared due to a chunk of DNA that went missing after our evolutionary divergence from chimps. The researchers have identified another DNA deletion that may have contributed to humans' bigger brains."

Comments

That would be useful.

[Anonymous Coward]

Because I'm good at irritating females, yet somehow it doesn't lead to their ovulating.

Occam's Razor

[argStyopa]

...because women, generally, don't want them? They by & large run the reproductive sweepstakes, even back in the "me big strong caveman, me conk woman on head" days when "consent" was a little more broadly interpreted.

And which came first, male lack of spines, or female concealed ovulation?

When analyzing the genetic record, how can one 'sort out' the distinction between DNA changes that have happened due to mutation, compared to the changes induced by broad and consistent female choice?

Re:Occam's Razor

[joocemann]

The female chooses the mutant. The two things are not separate. The mutant male had no spines, so she chose him. Her sons had no spines, so other fems chose them. Fitness at work.

" ... irritate a female into ovulating" ...???

[PolygamousRanchKid]

Most male mammals wield a penis covered with spines made of keratin, the same material that forms fingernails, to sweep out competitors' sperm and irritate a female into ovulating.

Human females are different. They get irritated when ovulating. Before, during and after, in fact.

Re:Huh?

[ColdWetDog]

I'd better go see a doctor.

Or a veterinarian.

Re:Huh?

[Kelbin]

What, you mean these spines on my penis aren't normal?

I'd better go see a doctor.

I think it means you should stop shagging hedgehogs.

Pearly Penile Papules

[deimios666]

Still in the genepool only very diluted: https://secure.wikimedia.org/wikipedia/en/wiki/Hirsuties_coronae_glandis

There's a lot more going on here

[smellsofbikes]

First off, human males *do* have a mechanism to sweep out sperm from other males, consisting of the most visually obvious part of the male penis and protracted mechanical movement. We lost spikes, we evolved something else to do the same function. Secondly, there are many other mammals that have different methods for accomplishing the same thing: male squirrels have something like superglue that forms a plug after coitus, to prevent other males gaining access afterwards. (And female squirrels have claws and quite a bit of expertise in removing those same plugs, as you'd expect in any good arms race.) Likewise, many male lizards and insects avoid the problem by just staying connected until the female is ready to lay her eggs, which puts a whole lot of stress on the female during that period: they both get eaten pretty often.

But if you really want to get weird, go look at insects like bedbugs, where males practice traumatic insemination: they don't go looking for an orifice, they make one, and let the female's body figure out what to do with the results. Or bees, where the barbs aren't there to stimulate ovulation but to make sure the penis breaks off and acts as a plug that can't be removed.

And the next step weirder is hermaphrodites, where mating is a contest in which both wish to inseminate the other without getting inseminated, so mating strategies get seriously complicated. (The phrase 'penis fencing' has been used.)

Anyone who is curious about this should read the brilliant book Promiscuity: the evolutionary history of sperm competition by Tim Birkhead. It will make you relieved to be human.