Science with Jonathan Webb: What did ancient Denisovans look like?

Henrietta Strickland
September 20, 2019

Denisovans lived alongside modern humans and Neanderthals 100,000 years ago, but until now, their appearance remained a mystery It's one of the most mysterious human ancestors in history, and now scientists have revealed what the Denisovans might have looked like. Now, for the first time, researchers have shared what they might have looked like. Their existence was only recently discovered and has fascinated scientists worldwide.

Previous surveys suggest Denisovan DNA accounts for between three and five percent of the genome of Melanesians and Aboriginal Australians.

But it has implications beyond Denisovans and human evolution. Because their DNA lives on in some humans today, researchers have reason to believe that they once lived all throughout Asia.

Reconstructed Profile of the Denisovan Skull.

Scientists may have been able to sequence their genome, but this small fossil record made it hard to piece together their appearance - until now.

By comparing DNA methylation patterns in Denisovans to those in modern humans, Neanderthals and chimpanzees, the team could infer which genes are dialled up or down in each group.

This process relies on extracting information from gene activity patterns, rather than DNA sequences.

"DNA methylation refers to chemical modifications that affect a gene's activity but not its underlying DNA sequence", explained Carmel.

Explaining the technique to Gizmodo, Stringer said the observed methylation patterns were "translated into predictions of how those patterns would affect certain developmental pathways, using genetically linked abnormalities in modern human anatomy as a check on the areas of the body affected, and where possible, the direction of change compared with the norm". They further analyzed the differences to determine how those might influence anatomical features.

The HU researchers were able to reconstruct the Denisovan profile over a three-year period by examining patterns of methylation in their ancient DNA.

The skeletal reconstruction, along with an artist's rendering of the 13-year-old girl's head and face, were published in the journal Cell.

Liran Carmel, an author of the study, said: "We provide the first reconstruction of the skeletal anatomy of Denisovans".

The researchers applied their DNA methodology to the Neanderthal and the chimpanzee and found that they predicted "roughly 85%" of the observed directional divergence.

"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", David Gokhman, now a postdoctoral student at Stanford University, said in a news release.

Denisovans and Neanderthals branched off some 400,000 to 500,000 years ago into two distinct branches, separate from the Homo Sapiens branch of modern humans. The bulk of those (36) were in the skull-the reconstruction suggests a Denisovan skull was wider and they had a longer dental arch. However, several features were found to be similar to those in early modern humans and Neanderthals, including an elongated face and wide pelvis.

While the research was being reviewed for publication, another study was released describing a Denisovan jawbone - which coincidentally, matched up with this study's prediction.

Neanderthals migrated into regions where Denisovans lived, said Erella Hovers, a prehistoric archeology professor at the Hebrew University. And the reconstruction is that of a young female Denisovan.

The findings show that DNA methylation can be used to reconstruct anatomical features, including some that do not survive in the fossil record.

Such DNA analysis can teach scientists about how our forerunners evolved and how their development differed, Mr. Carmel said in an email.

Other reports by Click Lancashire

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