In Alison Jolly's Lucy's Legacy: Sex and Intelligence in Human...
The enormous penis. Another peculiarity of humans is that the penis is twice the size for body weight as that of any other primate. Indeed, gorillas and orangutans are strikingly underendowed in thisI admire Diamond's book Why Is Sex Fun, but the idea that human penises are enormous because of men (straight men) needing to show off to other men, and not because they may provide more pleasure to females, is boyish.
respect. Among bonobos, the penis is longer than our own, but thinner. Male bonobos display a pink and obvious erection and go in for “penis-fencing." The two apes with most frequent sex, ourselves and bonobos, are the two with huge penises.”Jared Diamond concludes that the function of a large penis is to show off to other males. He may be influenced by his time in New Guinea, among people whose chief clothing is the exaggerated and erect penis sheath. It is true that men's genitalia seem to interest other men, in urinals and locker rooms, more so than women. But
the reproductive advantages of giving pleasure to females, promoting mate choice, and stimulating female orgasm by tactile means should not be underestimated.”
