An extinct branch of the human species that may have interbred with modern humans was discovered to be even more genetically diverse than another human race ancestor, the Neanderthals.

Scientists unearthed a finger bone and teeth in the Denisova cave in the Altai mountains of Siberia. The remains belonged to lost ancestors called Denisovans. The DNA retrieved from the bones revealed that it belonged to a young girl, who may have had the same origin as Neanderthals but has enough distinctions in her DNA.

"The ancient hominin population was more diverse genetically than Neanderthals, but not as diverse as modern humans," co-author Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology, and his colleagues said.

The genetic information gathered from the finger can help scientists understand more about the extinct human species. For example, further analysis of the Denisovan DNA showed that they have contributed at least 5 percent of their DNA to the genomes of modern day people from Oceania and around 0.2 percent of those of the Native Americans and Asians.

The contribution of Denisovan DNA could also be linked as responsible for some of the adaptive traits of the modern day man.

"In Tibet, an adaptation to live at high altitudes where there is little oxygen in the air has been shown to come from Denisovans," Pääbo said.

Aside from the bone, the scientists have also analyzed two molars found in the cave, which again had distinct characteristics differentiating it from the Neanderthals and modern man, as the teeth were large and lacked certain raised parts on their crowns. That molars were confirmed to be Denisovan when the DNA extracted from the teeth matched with the DNA from the finger bone.

Further analysis of the teeth revealed that the DNA from one of the molars had fewer mutations than the other one and the finger bone. This means that the other molar belongs to the order of the evolution line that is about 60,000 years older than the other two specimens.

The difference suggested that the Denisovans were most probably present in the Altai mountains for a very long time or at least, according to Pääbo, periodically.

In conclusion, while the Denisovans were not as genetically diverse as modern humans, they were still more genetically diverse than the Neanderthals.

The research is published in the journal Proceedings of the National Academy of Sciences.

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