Hind limbs. Complete ankles and toes. Those are not features that come to mind when thinking about snakes. But, those are the features of the most recent common ancestor of all snakes, according to new research.

“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, a Yale Ph.D. candidate. “Both of those insights resolve longstanding debates on the origin of snakes.”

Today, there are more than 3,400 species of snakes. You can find them in nearly any environment from arid deserts to oceans.

Lead author Allison Hsiang said this ancestral snake used stealth to hunt and was nocturnal. The snake likely called forested areas of the Southern Hemisphere home.

This habitat is probably why humans have always been so wary of snakes. These same forested areas were home to early humans who foraged for food.

Jacques Gauthier, a senior author of the study, touches on this. “Primate brains, including those of humans, are hard-wired to attend to serpents, and with good reason.”

Gauthier added, “our natural and adaptive attention to snakes makes the question of their evolutionary origin especially intriguing.”

To paint this new picture of snakes’ ancestor, the team of Yale researchers studied snake genomes, modern snake anatomy and looked at fossil records for clues.

These ancestral snakes were non-constricting and used needle-like hooked teeth to attack prey. The snakes originated during the middle Early Cretaceous period, about 128.5 million years ago – according to the researchers.

“Ancestral snakes are unequivocally inferred to have originated on land, rather than in aquatic settings,” the researchers write in their study.

Image credit: Julius Csotonyi, an artist rendering of an ancestral snake

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