A Serpentine ‘Explosion’ 125 Million Years Ago Primed Snakes for Rapid, Diverse Evolution – Smithsonian Magazine

The cat-eyed snake slithers in the Peruvian Amazon. Dan Rabosky, University of Michigan

Not long after the origin of snakeswhen certain lizards began to lose their legs more than 150 million years agoa burst of evolutionary innovation paved the way for the variety of serpentine shapes, sizes and behaviors we see today.

From 30-foot green anacondas in South America to four-inch Barbados threadsnakes you could mistake for a noodle, the roughly 4,000 snake species in oceans, freshwater, forests and deserts exemplify the many unique forms and functions the reptiles have achieved over millions of years of evolution.

Researchers have now helped shed light on this diversity, identifying an evolutionary explosion early in snakes history that helped them evolve at a rate about three times faster than contemporary lizards, according to a paper published last week in the journal Science.

The rate at which snakes evolve new features and evolve new kinds of diets has basically been kicked into overdrive, Daniel Rabosky, the senior author of the study and an evolutionary biologist at the University of Michigan, tells Scientific Americans Jack Tamisiea. Lizards are puttering around on a moped, while snakes are on a bullet train.

That accelerating moment, which occurred roughly 125 million years ago, is the type of evolutionary jump that Charles Darwin once called an abominable mystery, and what the research team refers to as a singularity. Essentially, instead of the typical slow crawl of natural selection, snakes experienced many small changes in quick succession. Over the expansive timespan of prehistory, these added up to a sudden shift in the direction of the animals evolution.

To illuminate the details of this time for snakes, the research team analyzed the genomes of more than 1,000 squamates (the order that includes snakes and lizards) and examined partial DNA from about 80 percent of all known snake and lizard species. They combined these findings with statistical models to create the most detailed evolutionary tree of lizards and snakes to date.

From this analysis, the team found that the singularity appeared to have coincided with key changes to snakes anatomy. Their skulls became flexible, better for attacking and swallowing prey; they developed the ability to detect airborne chemicals with their tongues; and they lost their legs, becoming thinner and longer, better for traversing new terrains.

We thought maybe theyd show something exceptional in one area but maybe not in another, Alexander Pyron, a biologist at George Washington University (GWU) and an author of the study, said in a GWU press release. But, no, its every single thingincreased rates of body form evolution, increased rates of diet evolution, increased rates of niche evolution. Snakes stand out as a huge cut above every other group of lizards.

By studying the stomach contents of more than 68,000 dead specimens, mostly from museum collections, the researchers also identified snakes as becoming early dietary specialists, evolving the ability to eat prey that other lizards didnt touchincluding vertebrates and some toxic, hard to digest creatures. Along the way, it surely didnt hurt their hunting prowess that some snakes evolved to see infrared light, and some became venomous.

The paper demonstrates that snakes are an evolutionary singularity that has changed the face of the Earth, Michael Lee, an evolutionary biologist at Flinders University in Australia who wasnt involved in the research, tells Scientific American.

Still, scientists have much to learn. The findings didnt pinpoint which of snakes several unique traits gave them such an advantage, why the sudden singularity occurred, nor exactly how their specialized diets may have contributed to such a rapid evolutionary pace.

Snakes are special and weird, Nick Longrich, an evolutionary biologist and paleontologist at the University of Bath in England who was not involved in the new study, tells Popular Sciences Lauren Leffer. I think that, here, theyve successfully quantified it.

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A Serpentine 'Explosion' 125 Million Years Ago Primed Snakes for Rapid, Diverse Evolution - Smithsonian Magazine