The shape of the penis head may have evolved to help remove rival sperm
A new study has found that the shape of the human penis head may have evolved specifically to aid in the removal of rival sperm during intercourse. Researchers from the University of Texas at Austin analyzed the shapes of different animals' penises and found that those with more spherical heads were better able to squeeze out competing sperm. This suggests that the human penis head may have undergone natural selection to become more pointed and conical, which allows for greater control and precision when removing rival sperm.
According to the researchers, this adaptation is thought to have arisen because it helps ensure paternity by allowing the male to more effectively "clean house" after mating. In many species, including humans, males compete for access to females through aggressive displays such as fighting or vocalizing. The winners get to mate with the female while the losers go unrewarded. As a result, they often leave behind their genetic material in the form of sperm that can fertilize her eggs if she becomes pregnant.
"We think the shape of the human penis head evolved to increase fertility," said lead author David Puts. "It gives men an advantage over other males who might want to impregnate the same woman."
The study involved examining the penises of various animals, including rabbits, lizards, and elephants. They found that those with rounder heads were less effective at removing competing sperm than those with more pointed ones. Human penises are relatively long and thin, but the head is fairly narrow and rounded, suggesting that we may not be as good at clearing out rival sperm as some other species. However, the researchers noted that our ability to use condoms could potentially help us overcome this disadvantage.
"Our findings suggest that the evolutionary pressures on the human penis are different from what we've previously assumed," said co-author Robert Dodds. "We don't need to be big or strong to impress women; instead, we need to be able to remove rival sperm more effectively during intercourse."