A Moment of Science

Scared Of Snakes

Do you jump when you see a snake? Some scientists think there could be an evolutionary explanation.

Close-up of a yellow and black snake

Photo: Jon David Nelson (flick)

If we're anything like macaques, we may have special neuronal circuits that are devoted to snake-detection.

Unless you’re a snake charmer, chances are when you unexpectedly come across a snake you freeze or quickly jump away. Why? It might be because our brains evolved to be particularly sensitive to spotting snakes.

Rodent-Like Mammals

Around 100 million years ago, the early evolution of rodent-like mammals coincided with the evolution of the first constricting, slithery snakes. According to some biological anthropologists, because those ancient snakes preyed on mammals, evolution selected for sharp vision in the subset of rodents that went on to become primates.

Those best able to see snakes and avoid them survived, passing on their genes including the ones responsible for keen eyesight.

Now, fast forward forty million years to when both venomous snakes and early monkeys were making their debut on the evolutionary scene. Similarly, nature selected for individuals best able to outwit snakes, thanks to strong vision.

Evidence In Macaques

And so, the theory goes, we’ve inherited our ancestors’ excellent eyesight and sensitivity to snakes.

Now, there may be other reasons why lots of people jump when they encounter a snake. And keep in mind that the theory we’re talking about doesn’t explain why some people fear snakes. That’s a different matter.

But there is some evidence that our ancient ancestors’ proximity to snakes has shaped our brains. Neurological studies of captive Japanese macaque monkeys, who’d rarely if ever seen a snake, have shown that their brains respond more quickly and strongly to images of snakes than to other images.

Read More:

  • Eek, Snake! Your Brain Has A Special Corner Just For Them (NPR)
  • Fear Of Snakes Drove Pre-Human Evolution (LiveScience)

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