What Did the First Snakes Look Like? New Evolutionary Analysis Offers Surprising Hints

A rare snake fossil, Archaeophis proavus. Raimond Spekking [CC by 4.0]/Wikimedia

People have long been fascinated by snakes. They feature prominently in our creation myths, hypnotize us with their sinuous locomotion, and invade our nightmares. But very little is actually known about snake evolution.

The reason? Snakes are mostly small — with a few exceptions — and their fragile skeletons don't leave many fossils. Large gaps therefore remain in our understanding of the snake evolutionary tree, and with such little hard evidence, theorists are left to speculate.

But a new analysis recently published by Yale University paleontologists promises to shed some light on these serpent mysteries, as well as shake up some of the prevailing theories, reports Phys.org.

"We generated the first comprehensive reconstruction of what the ancestral snake was like," explained Allison Hsiang, lead author the study.

By analyzing snake genomes, modern snake anatomy, and new information from the fossil record, researchers inferred that the most recent common ancestor of all modern snakes likely retained tiny hind limbs, was nocturnal, and had needle-like hooked teeth. Perhaps most surprising, this protosnake probably lived on land, in the forest. This finding flies in the face of the most widely accepted theory of snake evolution, that snakes evolved their long, serpentine body design as an adaptation to a marine environment.

"Our analyses suggest that the most recent common ancestor of all living snakes would have already lost its forelimbs, but would still have had tiny hind limbs, with complete ankles and toes. It would have first evolved on land, instead of in the sea," said co-author Daniel Field. "Both of those insights resolve longstanding debates on the origin of snakes."

Another surprise is that the protosnake is suspected to be non-constricting. Pythons and boas — generally considered to be more primitive among modern snakes — hunt and kill their prey through constriction. But this hunting strategy may have been a later development. It's also unlikely that the protosnake was capable of eating anything much larger than its own head, as many modern snakes are capable of.

Of course, it's impossible to know exactly what the common ancestor to all snakes looked like without a fossil of the creature, but through informed, reasoned imagination, we might narrow down the range of possibilities. At the very least, this new analysis will allow evolutionary biologists to hone their theories, as well as open the door to more precise speculation.