A tiny fragment of finger bone has enabled scientists to map out the entire genetic code of the Denisovans, a little-known ancient cousin of modern humans.
Evidence suggests that the Denisovans, who lived in Siberia around 50,000 years ago, had dark skin, brown hair and brown eyes.
Previous research has suggested they co-existed with Neanderthals and interbred with our own species, Homo sapiens.
The existence of the Denisovans was only confirmed in 2010. Scientists made the discovery after studying DNA from a piece of finger bone and two molars found at Denisova Cave in the Altai Mountains of southern Siberia.
On Thursday the same group reported results from full scale genome sequencing which produced a Denisovan genetic blueprint on a par with those obtained for modern humans.
The scientists found that the Denisovans were most genetically similar to Australian aborigines and island populations from south-east Asia. They listed about 100,000 changes in the human genetic code that occurred after Homo sapiens and Denisovans parted company on the path of evolution.
"This research will help determine how it was that modern human populations came to expand dramatically in size as well as cultural complexity while archaic humans eventually dwindled in numbers and became physically extinct," said lead scientist Professor Svante Paabo, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The research is published in the journal Science.
There are hints that both the Denisovans and Neanderthals emerged from a single population that migrated out of Africa. Modern humans are believed to have left Africa to colonise other parts of the world hundreds of thousands of years later. In time, Homo sapiens inherited the Earth while the Neanderthals and Denisovans became extinct.
The researchers also found that people from eastern Asia and South America possessed slightly more Neanderthal genes than those from Europe. This suggests that their ancient ancestors were more likely to have interbred with Neanderthals.