For Chimps, a Rear End Is Worth a Thousand Faces

Chances are, you’ve seen more than one guy on the street turn to stare at a woman’s rear end. Now it looks like men aren’t the only ones: A new study found that chimps can recognize other chimps simply by looking at photos of their butts. Well-known Emory University primatologist Frans de Waal discovered that chimpanzees could match up pictures of other chimps’ rear ends and genitals to pictures of the corresponding faces—though it only worked if the observer knew the photo subject personally. "They were not only seeing the photographs as representations of chimps they knew," says de Waal, "but linked the face and behind by drawing upon a mental representation of the whole body of those chimps." In a separate experiment, de Waal tested how well chimps can judge the sex of another chimp based on just a photo of the mystery chimp’s face. Again, the test chimps ...