Secrets of the Phallus: Why Is the Penis Shaped Like That?: Scientific American.

Results from a second questionnaire revealed that, upon first being sexually reunited after time apart, couples engaged in more vigorous sex—namely, compared to baseline sexual activity where couples see other more regularly, vaginal intercourse following periods of separation involve deeper and quicker thrusting. Hopefully you’re thinking as an evolutionary psychologist at this point and can infer what these survey data mean: by using their penises proficiently as a semen displacement device, men are subconsciously (in some cases consciously) combating the possibility that their partners have had sex with another man in their absence.