Post a photo of a live snake on social media and see what happens. Odds are, the comments will follow a common theme: “Kill it.” A photo of a one-foot garter snake basking on the edge of a dock and a full-grown rattlesnake ready to strike will often draw the same response:

“The only good snake is a dead snake.”

What is it about serpents, or even just photos of harmless ones, that draw such visceral reactions? As it turns out, there’s a scientific explanation. Ophidiophobia, the fear of snakes, was part of the evolutionary process that helped mammals survive.

Evolution
“The idea is that throughout evolutionary history, humans that learned quickly to fear snakes would have been at an advantage to survive and reproduce,” said Vanessa LoBue, a post-doctoral fellow in psychology at the University of Virginia, in an interview with Live Science. “Humans who detected the presence of snakes very quickly would have been more likely to pass on their genes.”

Fast forward thousands of years and that fear, however irrational, is still ingrained in our psyche. In fact, we are actually born with it, according to four European psychologists. To test that hypothesis, they showed photos of spiders and snakes to 6-month-old infants to see how they would react. The researchers also showed them photos of fish and flowers to compare reactions.

Not all of the babies had what researchers described as “pupillary dilations,” a standard physiological reaction to negative stimuli, when they saw photos of snakes. Enough did, however, to give scientists an idea of what’s going on: “Early attention biases and arousal to ancestral threats predispose humans to develop specific fears of these stimuli given appropriate direct or vicarious learning opportunities.”

But if only a fraction of children have an innate fear of snakes, why is the first impulse among so many adults to reach for a shovel, gun or steering wheel? Thanks to near-instant information at our fingertips, adults should know that snakes are, by and large, harmless. Still, killing snakes is widely practiced and widely accepted.

Personality and Religion
That could be because some folks have a dominionistic view of wildlife. That is, of the various attitudes towards wildlife, some hold a “dominance, physical control or mastery of wildlife,” according to Yale sociologist Dr. Stephen Kellert. He developed nine typologies that characterized people’s attitudes toward wildlife. Hunters were either dominionistic, utilitarian or naturalistic.

“Those who held more dominionistic worldviews indicated lower support levels for protecting the two-striped garter snake, Ozark big-eared bat, and Dolloff cave spider,” Kellert wrote, regarding attitudes toward three threatened species

Some have speculated that dominance view is religion based, specifically among Christians. The Bible mentions serpents or vipers about 80 times, typically as a metaphor for Satan or some other evil. In many of those instances, the serpent is killed, or is something that should be killed.

But not everyone who fears snakes is religious. Duke University master’s candidate Diego Calderon-Arrieta found no link between religion and a fear of snakes when he surveyed his fellow Nicholas School of the Environment students.

Could it be that some people just like killing things, even something as benign and unthreatening as a turtle?

Roadside Studies
One experiment conducted by Mark Rober and posted on YouTube found similar results. Rober, a self-described former NASA engineer and “friend of science,” placed a rubber turtle on the shoulder of a rural road and then hid in the bushes to observe. He alternated the turtle with a fake snake and a rubber tarantula.

Although 94% of the vehicles passed by without incident, 6% of drivers went out of their way to run over one of the three creatures. Only 1% of those struck the turtle, while nearly twice as many ran over the snake. A whopping 32% swerved to squash the spider.

Snakes Are Equally Scared of Us
The data shows, though, that the majority of snake bites are a result of people confronting the snakes, rather than the snakes confronting people.

An examination of rattlesnake bites in central Arizona found that 57% of all bites were a direct result of victims intentionally putting themselves at risk by trying to catch, kill or otherwise harass the rattlesnake. Also, more than 56% of those bite victims were drinking alcohol at the time.

Another study of snake bites in California found, “Rattlesnake bite is most common in young men who often are intoxicated and have purposely handled a venomous snake. The incidence of bites is highest in the spring and early summer months, and they most often occur in the afternoon. The hands and feet only are involved in 95% of all bites.”

In a different study, two sober researchers in South Carolina wanted to investigate the perceived aggressiveness of cottonmouths. To test this, they found cottonmouths in the wild and then either stood beside them, stepped on them, or reached for them with a prosthetic arm.

Of the 35 snakes they stood next to or stepped on, only one made a strike. The vast majority of snakes tried to escape or made defensive displays with no action. Of the 36 snakes that they tried picking up, 13 bit the artificial hand.

Their takeaway? If you leave snakes alone, then there’s no reason to fear them.

“Our observations strongly support the contention that snakes are first cowards, then bluffers, and last of all warriors.”

Feature image via Wiki Commons.