A 30,000-year-old fossil finger bone found in a Siberian cave belonged to a previously unknown strain of human, scientists say.
The surprising discovery came after researchers analysed unusually well-preserved DNA from the bone.
The findings, reported in the journal Nature, confirmed that the specimen came from a young girl who was neither “modern human” nor Neanderthal.
Instead she belonged to a separate, now extinct, branch of the human family tree scientists have named Denisovians, after Denisova Cave in southern Siberia where the fossil was found.
A molar tooth recovered from the cave is also believed to be from a Denisovian individual.
It looks different from the teeth of modern humans and Neanderthals, and more closely resembles those of much older human ancestors such as Homo erectus.
The finds alter the story of human evolution, suggesting the Neanderthals had an Asian sister group that broke away on their own evolutionary path before dying out.
Most scientists believe ancestors of the Neanderthals left Africa between 300,000 and 400,000 years ago to establish themselves in Europe and Eurasia.
Meanwhile, the direct ancestors of modern humans, Homo sapiens, remained and evolved in Africa.
They headed out of Africa 70,000 to 80,000 years ago and for a time co-existed with the soon-to-be-extinct Neanderthals.