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All snakes evolved from a few species that survived Cretaceous-period asteroid strike, study suggests

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By Christy Somos, CTVNews.ca Writer

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    TORONTO, Ontario (CTV Network) — A new study from the University of Bath in the U.K. suggests that all modern snakes evolved from a few species that managed to survive the giant asteroid impact that wiped out the dinosaurs and most living things at the end of the Cretaceous period, between 145.5 and 65.5 million years ago.

The Cretaceous period marked the last period of what’s known as the Mesozoic Era, following the Jurassic period and ended with the extinction of the dinosaurs.

The study, published in the journal Nature Communications, says that the mass extinction event of the asteroid strike was a form of “creative destruction” that allowed snakes to diversify their evolutionary processes, and that snake species began to diversify around that time.

Researchers, led by scientists at the University of Bath with collaborators from Bristol and Cambridge in the U.K. and Germany, used fossils and analysis of genetic differences between modern snakes to build a reconstruction of snake evolution, which helped pinpoint the time where modern snakes evolved.

The study results show that all living snakes, more than 4,000 species, trace back to a handful of species that survived the asteroid impact of 66 million years ago.

Researchers posit that snakes’ abilities to shelter underground and forgo food for long periods of time assisted them in surviving the destructive effects of the impact. The subsequent destruction of their competitors at the time from the strike allowed snake species back then to spread to new habitats and continents – spurring evolutionary processes.

That advantage allowed snakes to produce lineages like vipers, cobras, garter snakes and pythons, the study says, and notes that modern snake species, including tree snakes, sea snakes, cobras and boas, only emerged after dinosaurs’ extinction.

The study notes that there is a distinct shift in the shape of snake vertebrae in fossils from the period following the asteroid strike, which fed into the appearance of new species groups, including giant sea snakes up to 10 metres long, according to a release.

“It’s remarkable, because not only are they surviving an extinction that wipes out so many other animals, but within a few million years they are innovating, using their habitats in new ways,” said lead author Dr. Catherine Klein in the release.

The study also suggests that snakes began to spread across the globe during this time, and although the ancestors of living snakes “probably lived in the Southern Hemisphere,” snakes appear to have spread to Asia after the extinction event of the asteroid strike.

“Our research suggests that extinction acted as a form of ‘creative destruction’- by wiping out old species, it allowed survivors to exploit the gaps in the ecosystem, experimenting with new lifestyles and habitats,” said study author Nick Longrich in the release.

“This seems to be a general feature of evolution – it’s the periods immediately after major extinctions where we see evolution at its most wildly experimental and innovative,” he continued. “The destruction of biodiversity makes room for new things to emerge and colonize new landmasses. Ultimately life becomes even more diverse than before.”

Researchers also found evidence of a second diversification event around the time the earth shifted from a warm “Greenhouse Earth” into a cold “Icehouse” climate, which fomented the beginning of the Ice Ages and saw the formation of the polar icecaps.

The study says that the pattern researchers found in snakes’ evolution hints at how global catastrophes with severe and rapid environmental disruptions can drive evolutionary change.

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ctvnews.caproducers@bellmedia.ca

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