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About 50,000 years ago, the modern human being lived with others hominids such as Neanderthals –Of which we know a lot thanks to its numerous fossils found in Europe and Asia– and denisovans –Of which there are hardly any remains–.
The latter were discovered only a decade ago from the analysis of their DNA, contrary to the rest of human species identified thanks to their fossils. The Denisovan remains found - a phalanx of a little finger, three teeth, and a lower jaw - were too scarce to provide information on their appearance.
However, an international team of scientists, which has had the collaboration of the Tomàs Marquès-Bonet group, the Institute of Evolutionary Biology (IBE), a joint center of the Pompeu Fabra University (UPF) and the CSIC, has achieved rebuild what the mysterious Denisovans looked like starting from the tip of a little finger bone.
The study, led by the Hebrew University of Jerusalem (Israel) and published in the journal Cell, provides a first view of the anatomy of this little-known human population, based on the genetic data of the fossils that may have belonged to a Denisovan girl.
Reconstruction of the Denisovan hominid from DNA
The team applied a new genomic analysis technique to reveal for the first time up to 56 traits that characterize the Denisova hominid, 34 of them in the skull. The novel method makes it possible to associate changes in the gene regulation activity in fossils with anatomical changes between human groups to predict their physical appearance.
To do this, the researchers used information on the effect of monogenic diseases - affecting only one gene - on the anatomy of known hominid populations. The technique has thus made it possible to predict what these humans would look like only by analyzing the DNA of a little finger.
“For the first time we can get an idea of how were denisovans, only from molecular data ”, comments Tomàs Marquès-Bonet, ICREA research professor and director of the IBE, and one of the authors of the study. "In addition, this work is an example of how biomedical knowledge can be applied to evolution to help us decipher what our ancestors were like," adds the expert, also affiliated with the Catalan Institute of Paleontology Miquel Crusafont (ICP).
But then what did this mysterious population look like? "In many features they resemble Neanderthals, for example in their sloping forehead, elongated face and large pelvis," explains David Gokhman, first author and scientist at the Israeli university. "However, other features are particularly fascinating, such as its large dental arch and very wide skull, unique among hominids," he says.
To test the effectiveness of the method, the researchers first demonstrated that the technique accurately reconstructs the anatomy of widely described Neanderthals and chimpanzees. But at the time, the group did not have the first Denisovan jaw to have confirmed hominid appearance. This came later.
“One of the most exciting moments happened a few weeks after this article was submitted for review: Another team identified the first Denisovan jaw, so we compared the bone to our predictions to find that they matched perfectly. Therefore, without even planning it, we received independent confirmation of our ability to accurately reconstruct anatomical profiles based on a bit of DNA from the tip of a little finger ”, comments Professor Liran Carmel from HUJI, responsible for the study.
Denisovans' imprint on a pinky
Until now, DNA analysis had revealed that Denisovans mated with the ancestors of modern humans who live today in Australia, the Pacific Islands, East Asia, and Southeast Asia. Denisovan DNA likely would have contributed to the Tibetans' ability to live at high altitudes, and the Inuit's ability to live in polar regions, by interbreeding with populations in these regions tens of thousands of years ago.
Now, this study opens a window to understand how these hominids adapted to their environment and provides information on the traits that are unique to modern humans and those that separate us from this other extinct population.
Could these traits shed light on your lifestyle? Could you explain how Denisovans survived in the extreme cold of Siberia? There is still a long way to go to answer these questions, but this article demonstrates the power of combining biomedical data with evolutionary studies ”, concludes Marquès-Bonet.
Gokhman et al. "Reconstructing Denisovan Anatomy Using DNA Methylation Maps" Cell (2019).
The research has been promoted by “la Caixa”, the Howard Hughes International Career, the National Geographic Society and the Clore Israel Foundation, among others.