Is it true that natural selection caused the human penis to develop a ‘coronal ridge’, which serves in expelling other men’s semen from the vagina during coitus?
In an internal combustion engine, each piston is fitted with an oil ring, which has a slightly larger O.D. than the piston and serves to scrape oil off of the cylinder wall back into the crankcase on the downstroke, keeping it from entering the combustion chamber. Note that none of this applies to the Wankel.
Similarly, the human penis is equipped with a ‘coronal ridge’, which has a slightly larger O.D. than the shaft, which is reportedly capable of expelling any existing fluids, such as another man’s semen, from within the vagina, thereby preventing him from fertilizing her eggs.
Is this the reason why this ridge exists? Were early human females so promiscuous as to create a selection pressure for such a device??
Well… it’s been suggested anyway. Some mammals have developed plunger style penises to remove competitors’ semen. Other mammals (Raccoons for one I think) have semen that actually hardens somewhat to form a barrier inside the vagina. This prevents other semen from getting through to the uterus. The males of these species have developed a very hard pointy penis to break through the barrier.
I only saw this once on the Discover channel. And I think I only caught the last half hour…
I’ve also heard a suggestion that the female orgasm assists semen on its ‘journey’ - evolutionarily logical, in that a partner a woman wants to have sex with has a better chance of causing conception than one she does not want to be with.
I’ve also seen shows which suggest that is the case. It’s probably more correct to say that the penis is designed to scrape all semen out of the vagina rather than just other men’s semen. I don’t think a penis could make the distinction.
That could be an answer to why men feel like stopping after having an orgasm. Those cro magnum studs who kept going at it after an orgasm ended up scraping out all their semen, but the duds who fell asleep right away left it all inside.
Hooooooooooold on there a minute. (No pun intended.) Are you saying then that the penis of “early man” (whoever you want that to be) did NOT have the same illustrious design as we’ve all come to know and love? That, the process of women becoming promiscuous EVOLUTIONARILY (is that a word?) caused the penis design to change?
Well whatever the answer, kudos to the designer, because that ridge is one of my my favorite features! (Along with the vein that runs along base of the shaft.)
Well, well, well…it turns out that there has been serious studies into this: http://news.bbc.co.uk/2/hi/health/3128753.stm
Although I did find this response in a letter to the New Scientist:
So I guess it wasn’t much of a theory to the doctors in the provided link…but the “cornstarch” test must have been amusing nonetheless!!
Also…“They found the depth of thrusting was also important.” I completely agree.
And the fact that a doctor named “Dr. Colm O’Mahony” said “Maybe those missionaries knew something about position after all?” is also VERY funny to me!
I’ve only heard of the “scraping semen out” design for insects, not for “higher animals”.
And if it were true, then wouldn’t it make evolutionary sense for most animals to have such a ridge? From what I can recall (especially the infamous “penis poster”), this isn’t the case.
On top of which (you should pardon the experseeion), while a piston may have a ring to keep crankcase oil from getting into the combusion chamber, it would act to keep any oil that was in the combustion chamber already there, rather than “scraping it out”, wouldn’t it? I can’t understand the mechanics of the hypothetical “semen scraper” (and I don’t know how the insect version is supposed to work, or what it looks like). But I can’t for the life of me see how the coronal ridge will scrape out previously-deposited semen.
I may be missing something, but it seems unlikely to me.
Amusing… or disturbing:
*
“They tested their theory in experiments using latex phalluses, an artificial vagina and a mixture of starch and water.”*
Just imagine the poor grad student that had to go down to the local sex shop to buy this stuff!!! (I’m assuming dildoes weren’t amongst their normal lab inventory). Quothe the red-faced young male shopper pulling his hat down over his face:
“Uhhhm… m-m-m-might you gents carry artificial… um, hoo-has? I need one for… an experiment… at university… really.”
Then imagine the experiment it’s self. Three guys with clipboards standng around in lab coats and goggles watching a 70 year-old man ravaging a rubber snatch with a latex phallus and asking an assistant to pass the cum. Hope nobody walked in on that experiment!
I’m afraid to ask this, but … just for the purpose of comparison: do any other primate penises have this coronal ridge? Chimps, gorillas, monkeys, etc? Or is it peculiar to human males?
There was a book called “Sperm Wars” that suggested the “clean sweep” and others ideas that you might find interesting such as women are promiscuis to get both the best genetics and the best provided for their offspring. Maybe that’s where the idea came from…
There’s some interesting speculation here, some of it apparently done with a speculum. :eek: However, there can be no factual answer to the question. Anytime you ask a question about the purpose, design, or intent of some body part, you’ve stepped into the realm of guesswork.
