Slithering through Evolution

All about snakes and their weird debated evolution.

Snakes are a creature with a very debated history of evolution. Before recent years, most people thought of snakes to be descendants of mosasaurs, with some believing the legless reptiles to have come from burrowing lizards. But what’s the truth and where did they evolve from?

What Is Evolution?

Evolution is when a species adapts to their environment or certain circumstances, which can lead to entirely new species. Here, Homer explains...

Fossil Record

A fossil record is when a bunch of fossils are examined and collected to make a sort of timeline of a species’ evolution over millions of years. The snake’s fossil record is a little hard to complete. Snake’s fossils are uncommon because they’re small and frail, easily breaking during the process or becoming in complete.


DID YOU KNOW? Snake’s bodies are mostly just a really long torso (rib area) caused by evolution of the Hox gene.

The Evolution

The earliest modern snake fossils, without legs and classified as serpentes, is called a simoliophiids and is dated between 112 and 94 million years old!


Despite the debate between what snakes truly evolved from, marine or land animals, scientists have reached a consensus that snakes descended from lizards. Pythons and Boas, both more primitive groups of the species have vestigial hind limbs--which are really just tiny clawed digits, but they count. Two other snake types, Leptotyphlopidae and Typhlopidae, have remnants of a pelvic girdle.

The Debate

As stated, scientists believed that there were two options for where snakes came from: burrowing land lizards, or aquatic reptiles called mosasaurs.


For the aquatic reptile argument, their main evidence is that it would easily explain aquatic snakes. Also, a snake’s transparent eyelids could have adapted for combat in underwater conditions, and the ears lost from disuse. The snakes on land, according to this theory, would have moved to land during the Late Cretaceous period (65.5 million years ago).


Eventually, they would have evolved into the snakes we know today. A fossil was found to support this side of the argument. It was a 95 million year old lizard with tiny front legs, also being the earliest show of snakes evolving into limbless reptiles. It also suggests that front legs shrunk before back legs.

Against that, is the argument that snakes evolved from land burrowing lizards. Scientists say that in this case, their ancestors would be varanids in the Cretaceous period. The ones who support this theory say that it explains the transparent eyelids, internal ears, and why they lost their limbs. The transparent eyelids so they could see as they burrow, the internal ears so they can hear predators and prey, and the limbs so they can burrow easier. A fossil of an early snake relative supports this even further, being a two-legged burrowing animal with a sacrum (bone near the pelvis) and fully terrestrial.


Now, most scientists believe that snakes in fact did come from burrowing lizards, thanks to the discovery of tetrapodophis amplectus in 2015. It’s the first known snake fossil to have four limbs. It was a meat eating predator, and lived around 146 to 100 million years ago.

Quick Video On Snake Evolution

PL2: SNAKE EVOLUTION 1

Conclusion

So snakes are pretty cool with an interesting history. Their fossil record might not be fully complete, but scientists today have a pretty good idea of where and who they came from.


Let's not forget, they have also evolved to be able to become their own pillow. If that's not one of natures great works, then what is?