"It was a nice fit," she says. It seemed likely that primates
developed better vision because of snakes, not to reach out and
grab a piece of fruit. The problem with the old theory, she
says, is it doesn't mesh well with current neurological
evidence. The structure of the brain's visual system differs
among primates. Among primates with the best eyesight, the part
of the brain that is associated with fear is more "expanded"
than the part that is associated with "visually guided reaching
and grasping," Isbell says. That suggests that the evolutionary
changes in the primate brain resulted from predation. But she
admits neurology is not her cup of tea, and she's not confident
that neurologists will embrace her ideas any time soon. But
others have, including psychologists who see her theory as a
good explanation for why so many humans hate snakes, and
herpetologists, who know first hand of the awkward relationship
between primates, including humans, and snakes. So who's the
winner in all this? Us, if she's right.