Today's Snakes Evolved From a Few Survivors of Killer Asteroid

From the tiny garter snake in your backyard to massive green anacondas, all modern snakes evolved from those that survived the asteroid that wiped out the dinosaurs, a new study suggests.

There are somewhere around 3,700 species of snakes and they’re found on every continent except Antarctica. With that kind of diversity, it’s easy to think that their origins go way back to when they first started slithering on Earth, more than 100 million years ago, points out study corresponding author Nick Longrich from the Milner Centre for Evolution at the University of Bath in the United Kingdom.

But new research finds that today’s snakes have evolved from much more recent ancestors.

The asteroid impact that happened 66 million years ago destroyed about 76% of all species, including non-avian dinosaurs. Only a handful of snake species survived this Cretaceous-Paleogene event, the authors say.

Longrich and his colleagues believe the event was a type of “creative destruction.” Surviving snakes were able to fill the voids created by their lost competitors.

“Creative destruction is how environmental perturbations and extinction create openings for things to evolve, which can replace—or even increase—biodiversity. It’s sort of the reverse of the creative destruction of economists, where building something new (e.g. cars) wipes out the old (e.g. horse-drawn carriages),” Longrich tells Treehugger.

“It's possible that evolution sort of settles into a rut—once all the niches are full, it’s hard for anything new to come along—and by reshuffling things, sort of flipping the game board over, it resets things and starts everything evolving like mad again.”

How Some Snakes Survived

For their study, the researchers reconstructed snake evolution using fossils and genetic analysis to find the differences between modern snakes.

They found that all living snake species trace back to just a few species that survived the impact. The authors suggest snakes were able to survive the impact and its disastrous effects because they are able to shelter underground and exist for a long time without food.

“Snakes are good burrowers, and their burrows acted as natural fallout shelters, protecting them from extreme heat of the impact, or the cold of the impact winter,” Longrich says.

“Some snakes can eat subterranean invertebrates like termites, which were probably unaffected by the die-off of plants. Other snakes can feed very infrequently—taking a large prey item and then going six months or even a couple of years without feeding. So when food was scarce, they could get by.”

Because the asteroid event caused the extinction of so many of their competitors—including dinosaurs and snakes from the Cretaceous period—surviving snakes were able to move into new habitats, continents, and niches, the researchers say.

They also began to diversify. According to the findings, modern snakes—such as tree snakes, sea snakes, venomous vipers and cobras, and constrictors including boas and pythons—emerged after the asteroid event and dinosaur extinction.

The results were published in the journal Nature Communications.

“It was a bit surprising,” Longrich says of the results. “I had a hunch we might find something like this with snakes, but these models are a bit tricky—so I was surprised when it actually worked, and it seemed to suggest even fewer snakes survived than I would have assumed. I would have guessed that the ancestor of boas, pythons and cobras lived in the Cretaceous—we found it lived afterwards, and all these lineages diverged afterwards.”