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Your Fear of Spiders and Snakes Is Evolutionary, Baby

A study shows that fear is hardwired into everyone, even six-month-old babies.

You might have suspected this for a while, but your dumb, crippling fear of snakes and spiders isn't your fault. It's instinctual.

Scientists now have conclusive evidence to show humans have evolved with a hardwired fear of snakes and spiders. This has been the theory for years, but a new study reveals that such a fear exists in babies as young as six months old, who don't understand the potential dangers of either creature.


The study was a collaboration between researchers in Austria, Germany, and Sweden. A total of 48 babies from around Uppsala, near Stockholm, were shown either photos of spiders and flowers, or snakes and fish. Their stress levels were then gauged with an infrared pupil tracker, which measured the dilation of their pupils. What researchers found is that pupils expanded slightly when looking at flowers or fish, but dramatically when looking at spiders or snakes.

Professor Stefanie Hoehl, neuroscientist at the University of Vienna, explained why dilated pupils are so significant. "In constant light conditions this change in size of the pupils is an important signal for the activation of the noradrenergic system in the brain which is responsible for stress reactions," she told Science Daily. "Accordingly, even the youngest babies seem to be stressed by these groups of animals."

So why are babies getting worked up over snakes and spiders? The answer is probably in evolutionary programming. Stefanie Hoehl notes that our ancestors evolved alongside snakes and spiders for millions of years, which is long enough for the human brain to develop a hardwired response to such animals. "We assume that the reason for this particular reaction upon seeing spiders and snakes is due to the coexistence of these potentially dangerous animals with humans and their ancestors for more than 40 to 60 million years," she says.

Interestingly, other studies have found that similarly dangerous animals don't provoke the same response. Animals such as bears and rhinos don't seem to be red-flagged in the human brain, probably because we haven't shared the same environment for such a long time. As Stefanie Hoehl explains, 40 million years predates the existence of most modern, dangerous animals.

It's thought that between 1-5 percent of the population are clinically afraid of snakes or spiders, while around a third of all people report a "strong dislike." Now it seems the basis for this fear has a pretty conclusive root in evolution. So yeah, you're not being a baby. It's just instincts.