Samuel L. Jackson bemoaned the slithering serpent in the movie Snakes on a Plane. He “had it” with these snakes on planes.
What has not had it with snakes, however, is Earth.
But it was never a foregone conclusion that snakes would dominate Earth. In fact, if it weren’t for the Cretaceous mass extinction — yes, the same one that killed off most dinosaurs — we might not have any snakes at all.
In a study published Tuesday in the journal Nature Communications, scientists reveal that all living snakes can trace their lineage back to a few surviving species that emerged from the dust of the asteroid that devastated Earth 66 million years ago. This event formed the massive Chicxulub crater and set off a sequence of events that led to the extinction of 76 percent of Earth’s species.
These findings suggest snakes survived the mass extinction and later thrived because of the demise of other animals. They expanded into new areas across the globe, taking part in a phenomenon the researchers describe as “creative destruction.”
Creative destruction “is a bit of a reversal of the Marxist idea that creating things destroys other things,” Nick Longrich, a co-author on the study and a senior lecturer in evolutionary biology at the University of Bath, tells Inverse.
“Here, the destruction happens first, and that spurs creativity in evolution.”
What you need to know first — Why did some animals survive the Cretaceous–Paleogene (K–Pg) mass extinction event while others got wiped off the face of the Earth?
Scientists have long suspected snakes survived and diversified after the K-Pg extinction event, but due to the limited “fragmentary” nature of the snake fossil record, they weren’t able to prove it — until now.
How they made the discovery — A research team led by the University of Bath utilized unique methodology, combining fossil analysis with the sequencing of molecular data, to reach their conclusions.
“... one of the key drivers of evolution is actually extinction.”
“It is clear that integrating molecular sequence data and the fossil record can elucidate the influence of major events in Earth’s history on the evolutionary history of extant clades,” the researchers write.
Using these methods, the study team could track and observe the genetic differences between modern and ancient snakes.
What’s new — The researchers made three key findings:
- As few as six snake lineages may have survived the K-Pg extinction event 66 million years ago.
- After the K-Pg extinction event, surviving snakes successfully began to diversify into new lineages — like boas and vipers — and expanded into new regions, like Asia.
- The K-Pg mass extinction event was significant “in shaping Earth’s extant vertebrate faunas” or modern vertebrate animal life on Earth.
Why it matters — Snakes survived and expanded into new geographical areas because they could occupy new ecological niches in the sudden absence of other animals, which previously competed with snakes for resources.
“When you eliminate a huge number of species, you end up with a lot of empty niches,” Longrich says. “When you wipe out huge numbers of species, it sort of resets things, and evolution goes off in strange new directions, producing odd things, like human beings.”
Longrich and colleagues think their findings have huge implications for all vertebrate life on Earth — not just snakes. Similar species diversification patterns have occurred after extinction events across mammals, birds, and frogs.
“I think it’s significant not just for snakes, but more generally for evolution. I think the pattern we see in snakes is the rule, not the exception,” Longrich says.
He reasons that the biodiversity we see today is in part a result of the asteroid impact. Ultimately, Longrich believes these findings will help scientists better understand the very nature of evolution— the force driving life.
“I suspect one of the key drivers of evolution is actually extinction,” he explains. “It shakes things up.”
How did snakes survive the dinosaur asteroid?
After the asteroid’s impact, particles known as ejecta blanketed Earth.
“It got extremely cold after the dust and soot blocked out the sun,” Longrich says. This made it difficult for life to survive.
The cooling temperatures also caused a global collapse of photosynthesis, resulting in mass extinction across species.
But snakes had a trick hidden up their scales: their unique burrowing habits, which helped them survive wildly fluctuating global temperatures.
“Part of snakes’ survival comes down to the fact that most of them spend part of their lives in burrows,” Longrich says. “They could ride out much of the worst of the extinction.”
Other behaviors, such as the snake’s infrequent feeding habits and their ability to hunt at night — a behavior that would have served them well in the low-light conditions on Earth after the asteroid’s impact — may have also enabled their survival.
What’s next — The scientists have a whole slew of hypotheses to explain why snakes survived and diversified after the K-Pg extinction event. However, they still need a greater quantity of fossils to truly confirm any of these hypotheses.
“Unfortunately, the rarity of early Paleocene snakes makes it impossible to test this hypothesis. at present,” the study team writes.
So while snakes may be able to roam about in the night, we still remain in the dark about what exactly enabled the snake to become Earth’s ultimate survivor.
Abstract: Mass extinctions have repeatedly shaped global biodiversity. The Cretaceous-Paleogene (K-Pg)mass extinction caused the demise of numerous vertebrate groups, and its aftermath saw the rapid diversification of surviving mammals, birds, frogs, and teleost fishes. However, the effects of the K-Pg extinction on the evolution of snakes—a major clade of predators comprising over3,700 living species—remains poorly understood. Here, we combine an extensive molecular dataset with phylogenetically and stratigraphically constrained fossil calibrations to infer an evolutionary timescale for Serpentes. We reveal a potential diversification among crown snakes associated with the K-Pg mass extinction, led by the successful colonisation of Asia by the major extant clade Afrophidia. Vertebral morphometrics suggest increasing morphological specialisation among marine snakes through the Paleogene. The dispersal patterns of snakes following the K-Pg underscore the importance of this mass extinction event in shaping Earth’s extant vertebrate faunas.