BBC: Penis is a competitive beast
[A] team from the State University of New York believe the thrust of the penis during sex may help to clear a woman's reproductive system of a previous lover's semen.
Eeeew! We're entering into serious sicko territory here:
They tested their theory in experiments using latex phalluses, an artificial vagina and a mixture of starch and water.
These people are quite clearly bonkers (ahem). I wonder what they write in their CVs.