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Evolutionary psychology explores ancient and newer roots of instinctual fears

Just in time for Halloween, here are our picks for the scariest movies of all time.

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By Arthur Allen
Special to The Washington Post
Monday, October 25, 2010; 3:50 PM

Cars kill a lot more people than spiders, bats, snakes and wolves, but why don't we fear them in the same visceral way? When's the last time you saw a jack-o'-lantern carved in the shape of a BMW?

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The drugstore Halloween images of dark and hairy critters touch off sensations deep inside us, pointing bony fingers at instincts that go back millions of years, evolutionary psychologists say.

Although some of us fear snakes more than others, all baby humans, chimps and monkeys are equally jumpy when confronted with a black plastic snake. That aversion probably grew out of the pressures of life in the jungle eons ago. Back then, encounters with certain snakes were a matter of life and death, and a healthy fear of snakes kept our ancestors alive long enough to procreate.

In the field of evolutionary psychology, the belief is that instinctive fears became hard-wired in our biology, through genes or other inheritance, during the time (the Stone Age) and place (the African jungle and savannah) of our development into the Homo sapiens we are today.

But some new thinking suggests that these adaptations might date back before the Stone Age, and some, perhaps, to more recent times.

Much of evolutionary psychology is based on hard-to-test hypotheses about the past, which led the late paleontologist Stephen Jay Gould to dismiss the entire field of study as " 'just so' stories." But we aren't interested in the pros and cons of that argument. It's Halloween. Why not delve into the mysterious past with a bit of quavering, Vincent Price-like awe?

H. Stefan Bracha, former director of the Department of Veterans Affairs' post-traumatic stress disorder research center in Honolulu, did so in an article in the journal Progress in Neuro-Psychopharmacology & Biological Psychiatry.

Over the edge

Bracha's argument is that our mental settings evolved in different phases.

For example, some psychological traits are shared by all mammals. In experiments conducted in the 1960s, baby goats and baby humans were separately offered the opportunity to walk or crawl onto a transparent surface that gave the impression of walking off a cliff. Both declined.

Fear of heights is so widespread and understandable that psychologists consider it a normal fear. The common images of Halloween probably date to a slightly more recent period in evolution. Snakes and spiders killed simians in the African jungles where proto-humans branched off from chimpanzees about 20 million years ago. Another killer was the crocodile, which still hunts chimps in the Congo River basin.

Newborn rhesus monkeys are afraid of toy snakes and toy crocodiles - but not, say, of toy rabbits. Humans have no fear of Twinkies and cheeseburgers - au contraire - although these foods have become more dangerous to our health than anything that skitters, flits or crawls.

"We seem less prepared to develop phobias of things that threaten us in our immediate environment," says O. Joseph Bienvenu, a hospital psychiatrist and researcher at Johns Hopkins University. "You could put a gun in front of a monkey or a baby and they wouldn't go 'Ahhh!' like they would with a plastic snake. We're still catching up, if the evolutionary theories are right, with what we face today."


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