Sunday, September 03, 2006

Why are we so afraid of snakes?

Lynne A. Isbell, an anthropologist at UC-Davis, offers an evolutionary explanation, according to which "snakes, as predators, may have figured prominently in the evolution of primate vision — the ability, shared by humans, apes and monkeys, to see the world in crisp, three-dimensional living color." Here's a part of the evidence:

... [T]he monkeys with the sharpest eyesight tend to be those who live in greatest proximity to venomous snakes. About 60 million years ago, primates had branched into two groups: the Old World monkeys and apes (including us) and the lemurs of Madagascar. Around the same time, venomous — as opposed to constricting — snakes appeared in Africa and Asia. (Of all the predators of modern primates, snakes were the first to appear, about 100 million years ago.)

The Old World monkeys then branched again about 35 million years ago, when some went to South America and became the New World monkeys. The Old World monkeys and apes were the ones most exposed to venomous snakes, and of the three major primate groups, the Old World monkeys and apes have the best vision.

You might chalk this up to coincidence, but what if you learned that the Malagasy lemurs have the least complex visual systems of the primates, and that venomous snakes have never lived in Madagascar? ...