A new analysis conducted by Yale researchers revealed that the first snakes may have actually evolved on land, not in water. These proto-snakes were likely night hunters that might have had hind legs and even toes.

“We generated the first comprehensive reconstruction of what the ancestral snake was like,” said Allison Hsiang, lead author the study published online May 19 in the journal BMC Evolutionary Biology. Hsiang is a postdoctoral researcher in Yale’s Department of Geology and Geophysics.

Image via Smithsonian.

Snakes emerged about 128.5 million years ago, during the early Cretaceous. The Cretaceous was a period with a relatively warm climate, with high sea levels and numerous shallow inland seas. Some paleontologists proposed that snakes actually evolved in these seas, ultimately differentiating in the over 3,000 species we see today.

However, this study claims otherwise. Researchers integrated genetic sequencing and fossil analysis, adding it to the anatomical comparison of 73 lizard and snake species. With this, they believe they’ve created the most comprehensive snake family tree to date. Furthermore, they propose that ancestral snakes had sharp, needle-like teeth with which they grabbed small, rodent-like creatures and swallowed them whole.

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“We infer that the most recent common ancestor of all snakes was a nocturnal, stealth-hunting predator targeting relatively large prey, and most likely would have lived in forested ecosystems in the Southern Hemisphere,” Hsiang said.

But it gets even better – according to their analysis, the first snakes also had tiny hind limbs, and even toes.

“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.”

This was actually the most surprising result for paleontologists, but the science seems to back it up.

“I was most amazed by how strongly we inferred that the common ancestor retained hind limbs,” Field said. “Sometimes evolution plays out in unexpected and strange ways,” he added. “We think we’ve got a strongly supported idea, and based on the mathematical reconstruction it is what is most likely to be true.”

The study was published in BMC Evolutionary Biology.

Journal Reference: Allison Y Hsiang, Daniel J Field, Timothy H Webster, Adam DB Behlke, Matthew B Davis, Rachel A Racicot and Jacques A Gauthier. The origin of snakes: revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record, BMC Evolutionary Biology 2015. DOI: 10.1186/s12862-015-0358-5