DNA sequencing of a girl who lived 50,000 years ago in a Siberian cave has revealed the existence of a new group of ancient humans who were neither a Neanderthal nor a modern human.
The cave dweller turned out to be a Denisovan, cousin of the Neanderthals who were the closest extinct relatives of modern humans.
An international team of scientists led by Svante Paabo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany used a new method of genome sequencing to identify the group.
The team magnified the girl's single strands of DNA, a new method against the usual double strands DNA sequencing, which revealed that the girl had brown eyes, hair and skin.
"No one thought we would have an archaic human genome of such quality," said Matthias Meyer, chief researcher at the institute.
A comparison of the nuclear genome of the ancient girl and modern humans gave a "near-complete" picture of genetic changes that differentiate the living people from that of the Denisovans, who had close similarity to the Neanderthals. Both the groups were extinct nearly 30,000 years ago.
"For most of the genome we can even determine the differences between the two sets of chromosomes that the Denisovan girl inherited from her mother and father."
According to the researchers, Denisovan and modern human populations finally split between 170,000 and 700,000 years ago.
The Denisovans remained a mysterious group as they left behind little evidence about their existence for the paleontologists who discovered a tiny finger bone and two wisdom teeth in Siberia's Denisova cave in the Altai Mountains in 2008.