Sometimes the study is just so darn interesting, that even though it may not be directly useful, I think you’ll get a huge kick out of it.
This is such a study.
Here’s the deal.
It’s all about semen displacement and sperm competition.
It’s all due to the fact that women can have intercourse with multiple men.
So sperm competition evolved to meet the challenge.
Only the winner’s genes get transferred to a subsequent generation, so this is pretty important.
When a man ejaculates, the sperm swim around in the woman’s vagina and can live there for several days.
Some people think the sperm can live as long as five days.
If a woman has sex with multiple men a few days or hours apart, the live semen actually have to fight it out to see which sperm get to fertilize the egg.
It’s survival of the fittest on a microscopic scale.
So there are several interesting parts of the study.
One of them is that the penis itself can actually dislodge another man’s semen inside a woman’s vagina.
The shape of the penis, especially an uncircumcised penis, is designed to offset semen that may already be there.
It sort of digs it out with the thrusting and replaces the sperm with one’s own.
Circumcised men thrust harder and deeper in general, according to the study, by the way.
Even thrusting is different if a man suspects a woman has already had intercourse with a “competitor.”
The more vigorous and deeper thrusting serves the purpose of helping the penis dig out a competitor’s semen and replace it with one’s own.
Many sexually active males and females reported deeper and more vigorous thrusting when in-pair sex occurred under conditions related to an increased likelihood of female infidelity.
Also, during the ejaculation, although semen seems like it’s just a liquid, it’s so much more than that.
The ejaculatory fluid that comes out at the beginning is very different than that the comes out at the end.
The first part of the ejaculate does not typically coagulate, only the last fraction.
At the beginning of the ejaculation, the fluid is quite liquid.
It’s designed to be runny so that it can seep into a woman’s cervix and fertilize the egg.
The semen that ejaculates at the end of the ejaculation/orgasm is designed to clot or coagulate quickly.
So it kinda forms a block to any other semen that may be entering the woman’s vagina…
as a sperm competition tactic that functions to block sperm from rival males.
They call this a “copulatory plug.”
Wow. Just wow.
And if the man hadn’t ejaculated for a few days, his semen coagulated much faster.
This is all out of this amazing study.
I’m not sure if it’s all that useful, but it sure is interesting, don’t you agree?
Who would’ve thought that our penises were a digging tool and that ejaculatory fluid had such amazing qualities?
Citations
Semen Displacement as a Sperm Competition Strategy in Humans
http://evp.sagepub.com/content/2/1/147470490400200105.full
Dr. Lindemann’s Fun Sperm Facts!
http://www2.oakland.edu/biology/lindemann/spermfacts.htm
Click for more information on Sperm, for information on Men’s Health, or for more on Sperm Facts.