Fossil finger points to a surprising link between humans and Denisovans
New findings suggest Neanderthals evolved their unusually broad fingers after they split from Denisovans, just 400,000 years ago.
A replica of a fragment of a Denisovan finger found in Denisova Cave, Siberia, in 2008. Image Credit: Thilo Parg, Wikimedia Commons
In the not-so-distant past, Earth was chock full of different human species. As recently as 50,000 years ago, our Homo sapiens ancestors shared the planet with several other distinct early humans, including Neanderthals and Denisovans. That’s not the case anymore—but researchers are still uncovering their fair share of surprises about our long-lost cousins.
Here’s the latest reveal: Although Denisovans’ DNA ties them more closely to Neanderthals, their fingers may have looked more like ours. The discovery, described in a paper published this week in the journal Science Advances, suggests Neanderthals developed their unusually broad digits after their lineage split off from the Denisovans around 410,000 years ago.
The finger fragment—the tip of the right pinky of a 13-year-old girl—is the smallest of the five skeletal fossils known from Denisovans, which also include three molars and a partial jaw bone. It’s also been through quite the archaeological rollercoaster.
After it was unearthed from a cave in Siberia in 2008, the fossil was photographed, then split in half and sent to two different labs for analysis. Then, somewhere along the way, the original images of the bone went missing, stripping researchers of the only data capturing its intact shape.
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In the eight years since, however, scientists have managed to piece together a reconstruction of the fossil from photographs taken of both halves. (DNA extracted from both bits also confirmed that they were definitely from the same source.) After the pieces were virtually reunited, a team led by Eva-Maria Geigl of the Paris Diderot University in France stacked the digital finger up against similar bones from Neanderthals and modern humans. The results suggest that, like ours, Denisovan pinkies were fairly slender, with narrow, elongated tips—a far cry from the more robust, thick-tipped fingers of Neanderthals, Geigl told Ruth Schuster at Haaretz.
For the researchers, this was a bit of a shock. “I always expected [this] end of the finger to look rather Neanderthal-like,” study author Bence Viola of the University of Toronto told George Dvorsky at Gizmodo.
It’s worth noting that a single finger fragment from a young woman can’t necessarily speak for the hands of an entire population, Katerina Douka, an anthropologist from the Max Planck Institute for the Science of Human History who wasn’t involved in the study, told Dvorsky. Future finds may rewrite the story once again. Still, she says, the fossil in this “important study” clearly falls much closer in line with the fingers of modern humans.
This unexpected similarity doesn’t mean that Denisovans were anatomically identical to modern humans, though. Other Denisovan fossils, which include some exceptionally large teeth, bear far more similarities to lineages more ancient than ours.
In other words, the Denisovan physique was probably a mosaic of sapiens and not-so-sapiens traits—but it’s hard to know the exact ways in which this manifested, given how few fossils researchers have found so far. For now, a probable evolutionary portrait is this: Everyone’s fingers looked relatively similar through two splits—one in which modern humans and Neanderthals diverged, around 800,000 years ago (though this remains a topic of debate), and another, when the Denisovan line branched off from Neanderthals roughly 400,000 years later. Only after this point, it seems, did Neanderthals acquire their more distinct digits.
The virtually reconstructed Denisovan finger fragment, viewed from the back (A) and front/palm side (B) Image Credit: Bennett et al., Science Advances, 2019
That means Neanderthals may have evolved some of their hallmark features somewhat late in the game—perhaps due to changing environmental pressures at the time. It also implies that modern human fingers aren’t all that, well, modern, Jean-Jacques Hublin, an anthropologist at the Max Planck Institute for Evolutionary Anthropology who wasn’t involved in the study, told Dvorsky. Rather, our digits were a part of the ancient blueprint from which Neanderthals deviated.
All this perhaps underscores the idea that Homo sapiens shouldn’t be seen as a final evolutionary “destination”—and that their predecessors weren’t necessarily primitive. After all, modern humans still carry bits of Denisovan and Neanderthal DNA. This finger, then, may be the latest piece of the puzzle that points to what many early humans had in common, rather than what set them apart.
