I'll see you when I fall asleep

Bering’s mentor, Gordon Gallup, came up with an explanation after experimenting with a polyurethane vagina bought from a sex shop, a collection of facsimile penises and a bowl of cornflour batter designed to simulate sperm. Working feverishly, Gallup proved that if used as a plunger, a human penis is capable of cleaning out more than 90 per cent of sperm deposited inside the vaginal canal by a previous partner, far more than any other penis design. Gallup speculates that the penis evolved its shape because it lessened the chances of one becoming the unwitting surrogate father to another man’s kid.