Denisovan DNA analysis reveals face of mysterious human relative
The human family tree has many twisting branches, and we don’t fully understand most of them. One of the most enigmatic are the Denisovans, who were only discovered in 2008 and have been described from a few scattered bone fragments and DNA. That means we don’t really know what they looked like, but now researchers have managed to reconstruct a Denisovan face for the first time, thanks to DNA methylation mapping techniques.
The Denisovans occupied Earth at the same time as modern humans and Neanderthals. But while we know quite a lot about the latter, the Denisovans remain shrouded in mystery, thanks to a lack of fossil evidence. All we have are a few teeth, a finger, a jawbone and some other fragments.
But now, using DNA recovered from that finger bone, researchers from the Hebrew University of Jerusalem have reconstructed the face of a young Denisovan woman. Perhaps unsurprisingly, she turned out to have a mix of both modern human and Neanderthal features, as well as some unique to them.
According to the reconstruction, the Denisovans had wider skulls than either of the other species, and no chin. They had a large dental arch like us humans, but longer faces, larger pelvis and a sloping forehead much like Neanderthals. All up, they found 56 anatomical features that differed from us and Neanderthals, 34 of which were in the skull alone.
"We provide the first reconstruction of the skeletal anatomy of Denisovans," says Liran Carmel, lead author of the study. "In many ways, Denisovans resembled Neanderthals but in some traits they resembled us and in others they were unique."
The team came to these conclusions by studying what’s known as DNA methylation maps. Methylation is an epigenetic mechanism that changes what certain genes will do, without affecting the underlying sequence. They started by comparing the methylation patterns of humans, Neanderthals and Denisovans to see what was different. Then, they checked what those differences might mean, based on what happens in certain disorders where those genes stop functioning.
"In doing so, we got a prediction as to what skeletal parts are affected by differential regulation of each gene and in what direction that skeletal part would change – for example, a longer or shorter femur bone,” says David Gokhman, co-lead author of the study.
To make sure the predictions were accurate, the team first conducted the process on the DNA methylation maps of Neanderthals and chimpanzees – the appearances of which are obviously already known. They found that the technique was able to correctly predict about 85 percent of the anatomical features, giving them a decent confidence that the resulting Denisovan face is fairly accurate.
This was even backed up later. The team says that a few weeks after the paper was sent off for peer review, another paper was published describing a Denisovan jawbone.
“We quickly compared this bone to our predictions and found that it matched perfectly,” says Carmel. “Without even planning on it, we received independent confirmation of our ability to reconstruct whole anatomical profiles using DNA that we extracted from a single fingertip."
A similar DNA technique has been used in recent years to reveal that early Brits had much darker skin than previously thought. Of course, finding a complete Denisovan skull will help scientists reconstruct the species’ face more accurately, as was recently done with the oldest human ancestor.
The research was published in the journal Cell.