Complete Denisovan Guide: Appearance, Extinction, Neanderthal Links
Who were the Denisovans?
In short: even scientists are not sure. In a bit longer: The Denisovans are an extinct relationship with modern humans who lived in Siberia and East Asia. Some experts have argued that Denisovans are an entirely new species to our genus, Homo, but others think they are just East Neanderthals.
Unfortunately, it is difficult to know the exact period during which they roamed our planet because very few Denisovan fossils have been found. However, the fossils available to us indicate that they inhabited the Denisova cave in southern Siberia (hence “Denisovans”) 50,000 to 200,000 years ago. Additionally, a partial Denisovan mandible discovered in a cave on the Tibetan plateau indicates that they could be found in the area at least over 160,000 years ago.
These findings suggest that the Denisovans were contemporaries of the Neanderthals and even Homo sapiens (which first appeared about 300,000 years ago). In fact, DNA evidence suggests that the Neanderthals and Denisovans both lived in Denisova Cave, although probably not at the same time.
How were the Denisovans discovered?
The Denisovans were the first group of humans to be discovered on the basis of their DNA alone. However, this was largely by accident. In 2010, German geneticist Professor Johannes Krause (then a doctoral student) extracted mitochondrial DNA from what he believed to be a Neanderthal finger bone found in the Denisova cave. It wasn’t Neanderthal. Rather, Krause had stumbled upon a new line, the Denisovans.
This discovery left researchers in the bizarre and unprecedented position of having sequenced the entire Denisovan genome without having a single significant Denisovan fossil other than a few small bone fragments, a few teeth, and a small bone.
Then, in 2019, the right half of a mandible found in the 1980s in the Baishiya Karst cave on the Tibetan plateau was analyzed. Although no ancient DNA could be extracted from it, protein analyzes indicated that it was Denisovan.
Many suspect that a number of East Asian hominid fossils are also from Denisovan and have been misclassified as other species. But without successful analyzes of DNA or protein – and a few Denisovan fossils to compare them with – we just don’t know.
What did the Denisovans look like?
Even with hundreds of fossils, we still have a lot of questions about what Neanderthals looked like – imagine what that looks like with a species only discovered in 2010 without even a partial skull to their name!
But while it’s incredibly difficult to determine what the Denisovans looked like, there are a few clues. The few fossils available to us suggest that the Denisovans had large teeth, a large stocky jaw, and possibly a flattened, broad neurocranium (brain box).
Surprisingly, their appearance can be partly recreated thanks to a new technique using DNA methylation. Rather than examining the DNA itself, this promising (but contested) method does not look at the DNA itself in itself, but the activity of DNA and the way it is expressed. Using this, scientists predict that Denisovans have a large pelvis, large rib cage and joint surfaces, a low forehead, and a wider skull.
Have they ever mated with Neanderthals?
Yes! In fact, a small 2.5cm bone fragment found in Denisova Cave in 2012 caused a stir. At first he was unrecognized, hiding alongside thousands of animal bone fragments for four years. However, after being identified as a hominin bone by researchers at the University of Oxford, it was sent to the Max Planck Institute for further analysis.
The end result: In 2018, this 90,000-year-old bone was announced to belong to Denny (as it was affectionately known), a daughter who had a Neanderthal mother and Denisovan father.
How unlikely is it that with just over a dozen extant Denisovan fossil fragments one belongs to such a “hybrid”? Was it fluke or did such a mating happen all the time?
Why did the Denisovans die?
We don’t know exactly how the Denisovans became extinct, without any evidence of an environmental disaster. It is certainly possible that Homo sapiens surpassed the Denisovans, but, again, there is no evidence here.
We don’t even know when the Denisovans went extinct, with limited DNA evidence even suggesting that they may have survived in New Guinea or its surrounding islands until 15,000-30,000 years ago.
However, we know that Homo sapiens repeatedly mated with Denisovans – and that this cross has benefited humans today. For example, the variant of the EPAS1 gene that modern Tibetans and Sherpas inherited from the Denisovans makes them better suited to living at high altitudes, protecting them from hypoxia (a condition where the body’s tissues are deprived of oxygen) .
Likewise, scientists have even discovered that certain modern populations in Oceania have an immune system partly encoded (and strengthened) by DNA acquired from Denisovans.
About the Author – Ella Al-Shamahi
Ella is an explorer, television presenter and author of The handshake: a compelling story (£ 10.99, profile books).
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