Earth's First Snake Likely Evolved On Land, Not In Water Genetic sleuthing and comparisons of recently discovered fossils with living snakes point to a "protosnake" ancestor that likely had tiny hind legs and lived about 120 million years ago.

Earth's First Snake Likely Evolved On Land, Not In Water

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STEVE INSKEEP, HOST:

We have news this morning on the origin of snakes. Some scientists are changing their views about the evolution of these creatures that make many people cringe. They used to think snakes evolved in water, streamlined for swimming. NPR's Nell Greenfieldboyce reports on the findings of a new study.

NELL GREENFIELDBOYCE, BYLINE: When scientists want to know what life was like millions of years ago, they look at fossils. But that hasn't helped them much with snakes. Allison Hsiang is a researcher at Yale University.

ALLISON HSIANG: For a long time, there weren't very good snake fossils and things that sort of told us what snakes looked like early-on or transitional fossils between snakes and their closest ancestors.

GREENFIELDBOYCE: That's because snakes are mostly small with fragile skeletons that aren't easily preserved, although there are some notable exceptions.

HSIANG: There are some fossil snakes that get enormous. There's a fossil snake called Titanoboa that lived about 60 million years ago and it could get upwards of 40 feet in length.

GREENFIELDBOYCE: In the last decade, scientists have discovered a bunch of new snake fossils. Hsiang and some colleagues decided to do a rigorous comprehensive analysis to see what the most recent common ancestor of all snakes might have looked like. The team studied fossils plus the genes and anatomy of living snakes.

HSIANG: We had a total of 73 species, and I believe 15 of those were fossil species.

GREENFIELDBOYCE: Their conclusions appear this week in the journal BMC Evolutionary Biology. Hsiang says the evidence suggests that all snakes are the descendants of a kind of ancestral proto-snake that lived about 120 million years ago on land, not water. And this snake likely had tiny hind legs, left over from an even earlier ancestor.

HSIANG: They probably weren't using them in locomotion in any way, but they did probably still have vestigial hind limbs stuck in the back of their bodies.

GREENFIELDBOYCE: These ancient snakes probably slithered at night across the forest floor. They also had needle-like hooked teeth that they used to grab small rodent-like critters, which they swallowed whole. Nell Greenfieldboyce, NPR News.

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