It could function to reduce a young mans potential to father a child with an older mans wife, he says.
Sperm competition theory predicts that males will evolve ways to ensure that their sperm, and not another males, fertilises a females eggs.
READERS: The latex genitalia study wasn't terribly convincing because the models were circumcised, and in real life the foreskin would interfere with the semen-displacing functions of the coronal ridge.
Younger men, he says, willingly submit to having their reproductive ability reduced because they benefit socially from the older men, by forming alliances, and by gaining access to weapons or tribal lore.
The older men have also gone through the ritual, and seen their own reproductive effectiveness reduced.
By Kurt Kleiner Circumcision and other forms of male genital mutilation have always been a puzzle.
The ritual mutilations can leave the man vulnerable to infection and even death.
It might also be the case that selection works at a group level, so that societies that enforce mutilation are more stable because of less conflict over paternity, Wilson says.