In the field of evolutionary psychology, the thought is that instinctive fears become hard-wired in our biology through genes or other inheritance. A new study suggests that the fear of spiders and snakes has been shaped by evolution, stretching back to a time when early man slept on the ground or in caves and had to survive in an environment dominated by arthropods and reptiles.
Certain stimuli are pre-wired in the brain because they have been perennially dangerous to our ancestors. Although some of us fear snakes more than others, baby humans, chimps and monkeys are equally jumpy when confronted with a black plastic snake. That aversion probably grew out of pressures of life in the jungles and savannas of Africa eons ago. Back then, encounters with poisonous snakes or spiders were a matter of life or death, and a healthy fear of snakes helped our ancestors live long enough to procreate.