Humans hard-wired to recognise snakes?

Snakes tend to arouse sharp fear in humans, monkeys and apes as specific brain cells fire off a rapid warning for slithery danger, scientists have found.
Researchers show that there are specific nerve cells in the brains of rhesus macaque monkeys that respond to images of snakes.
The snake-sensitive neurons were more numerous, and responded more strongly and rapidly, than other nerve cells that fired in response to images of macaque faces or hands, or to geometric shapes.
Lynne Isbell, professor of anthropology at the University of California, Davis said she was surprised that more neurons responded to snakes than to faces, given that primates are highly social animals.

"We're finding results consistent with the idea that snakes have exerted strong selective pressure on primates," Isbell said.
In her previous study, Isbell argued that our primate ancestors evolved good, close-range vision primarily to spot and avoid dangerous snakes.

Modern mammals and snakes big enough to eat them evolved at about the same time, 100 million years ago.
Venomous snakes are thought to have appeared about 60 million years ago - "ambush predators" that have shared the trees and grasslands with primates.
Previous researchers have used snakes to provoke fear in monkeys, he noted. When Hisao Nishijo at Toyama University, Japan heard of Isbell's theory, he thought it might explain why monkeys are so afraid of snakes.

"The results show that the brain has special neural circuits to detect snakes, and this suggests that the neural circuits to detect snakes have been genetically encoded," Nishijo said.
The monkeys tested in the experiment were reared in a walled colony and neither had previously encountered a real snake.
"I don't see another way to explain the sensitivity of these neurons to snakes except through an evolutionary path," Isbell said.
The study was published in the journal Proceedings of the National Academy of Sciences.