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DNA from a Huge Tooth Confirms a New Ancient Cousin

The Denisovans may have co-existed and interbred with Neanderthals and Homo sapiens

The first Denisovan tooth that was discovered in 2008 (David Reich/Nature)
smithsonian.com

DNA extracted from a fossilized tooth, confirmed the presence of one of our elusive ancient cousins only recently discovered, the Denisovans.

These ancient relatives lived in the Caucasus mountains tens of thousands of years ago. And recent DNA tests show that the Denisovans—named after the Siberian cave their remains were discovered in—co-existed and even likely interbred with Neanderthals and early Homo sapiens, according to a paper recently published in the Proceedings of the National Academy of Sciences.

Likely cousins of Neanderthals and Homo sapiens, these hunter-gatherers suggest that our lineage may be much more complicated.

“The world at that time must have been far more complex than previously thought,” study author Susanna Sawyer tells Michael Greshko for National Geographic. “Who knows what other hominids lived and what effects they had on us?”

Until recently, scientists relied on what genetic information they could glean from a single Denisovan tooth and finger bone discovered in 2008. But after a second tooth was recently uncovered and analyzed, everything they knew about our ancient cousins changed.

The new tooth, called “Denisova 8,” appears to be at least 110,000 years old, roughly 60,000 years older than the other two specimens. The Denisovans were more closely related to Neandethals, having diverged from Homo sapiens about 500,000 years ago. Yet genetic scans suggest that Denisovans interbred with both Neanderthals and Homo sapiens, as well as possibly a fourth unknown species, Sarah Kaplan writes for The Washington Post.

That suggests that the early human world “was a lot like Middle-Earth,” as molecular anthropologist Todd Disotell, who was not involved in the new study, tells Carl Zimmer for The New York Times.

“There you’ve got elves and dwarves and hobbits and orcs,” Disotell says. When our species was still fairly young, “we had a ton of hominins that are closely related to us.”

Paleontologists still don’t know exactly what the Denisovans looked like, but they did have teeth so big that at first they were mistaken for cave bear teeth, Kaplan writes. Now, scientists are combing through the region to track down any more Denisovan fossils, as well as any hints of the unknown fourth species that our ancient cousins might have interbred with.

This new discovery also adds greater intrigue to the fossilized human teeth recently discovered in southern China, according to Kaplan. Genetic testing of those fossils will show whether or not they belong to the elusive Denisovans after all.

“It feels a bit surreal,” Sawyer tells Greshko. “Sometimes when I'm sitting in the clean room, I stop to think about how crazy it is that I am holding one of the only remains known to date from a new and mysterious hominid group.”

About Danny Lewis

Danny Lewis is a multimedia journalist working in print, radio, and illustration. He focuses on stories with a health/science bent and has reported some of his favorite pieces from the prow of a canoe. Danny is based in Brooklyn, NY.

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