They hiss and they slither, but they pose less of a threat to our lives thancars or ovens. So why do snakes set off more clinical fears and phobias than knives and guns?

Here's one scientific theory: Humans and other primates are predisposed to acquire fears of critters that once threatened our ancestors' lives.

Psychologist Susan Mineka. of Northwestern University contends that we have a predisposition to such memories" because our ancestors once had to face snakes, certainly more so than, say, ovens. Because they survived, those who rapidly acquired the fear were most favored in natural

Mineka, along with University of Wisconsin psychologist Michael Cook, put the theory to a test in six rhesus monkeys. Reared in the lab, the animals had no prior exposure to snakes. The psychologists showed a videotape of wild-reared monkeys reacting with horror to snakes. Within 24 minutes, the lab monkeys acquired a fear of snakes.

The psychologists then edited fake flowers, a toy snake, a toy rabbit, and a toy crocodile into the video. Tests later showed that after 40 to 60 seconds of exposure to each object, the monkeys feared only the toy snakes and crocodiles. Of the four objects, only snakes and crocodiles preyed on our ancestors. Coincidence?

Meanwhile, the search for evidence continues. The next time snakes inhabit your nightmares, ask whether it's that viper horror you watched, or are you just connecting with the fears of your forefathers.

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