Why the Sabertooth Went Extinct: Nanodiamonds Tell the Tale

If you have ever visited the Museum of Natural History in New York City, you have likely been awed at the size and power of some of North America's now extinct mammals. Massive mastodons, car-sized ground sloths, and ferocious saber-toothed cats plodded American ground tens-of-thousands of years ago. And then, seemingly overnight, they all disappeared.

While not as dramatic as the mass extinction of the dinosaurs, this 13,000-year-old die-out has left experts scratching their heads for generations.

Now, a team of researchers are suggesting that an extraterrestrial impact played a huge part in the extinction of these large mammals, citing exceptionally small diamonds as a key clue.

No, diamond-toting green men didn't crash land on Earth thousands of years ago, but according to new study published in the Journal of Geology, it's likely that a comet did.

"We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nanodiamonds, the production of which can be explained only by cosmic impact," author James Kennett said in a recent release. "We have also found YDB glassy and metallic materials formed at temperatures in excess of 2200 degrees Celsius, which could not have resulted from wildfires, volcanism or meteoritic flux, but only from cosmic impact."

The Younger Dryas boundary (YDB) is often seen as the thin dark layer of soil that is located only a few meters below the Earth's surface. Traditionally, this portion of the Earth could not form diamonds, despite its richness in carbon, simply because the formation of diamonds takes an incredible amount of heat and pressure.

However, the impact of a comet crashing into the Earth could certainly change things up.

Kennett and his team suggest that when a comet collided with the Earth, the resulting impact threw superheated soil over nearly a tenth of the planet, creating the YDB layer and lacing it with the formation of telltale nanodiamonds.

This cosmic impact also created sudden and severe environmental stress, where once flourishing ecosystems would have likely been too weak to support massive mammals such as the giant ground sloth.

Interestingly, scientists know of only one other layer laced with nanodiamonds on Earth. It's the well-known Cretaceous-Tertiary boundary from 65 million years ago, which is marked by the mass extinction of the dinosaurs - an event highly suspected to have generously helped along by a meteorite impact.