Denisovans are members of newly discovered species of hominin - the group of animals that includes humans, chimpanzees and bonobos.

Researchers learned of the existence of Denisovans when, in March 2010, a pinky bone from a young Denisovan, probably aged between five and seven, was discovered in Denisova Cave in Alta Krai in southern Siberia.

Carbon dating of artifacts, including a bracelet, that were found in the cave, showed that the owner of the pinky bone, who became known as X-woman, probably lived between about 30,000 and 50,000 years ago.

DNA from X-woman's mitochondria (structures in cells that are involved with energy, respiration and growth) was compared to the mitochondrial DNA (mtDNA) of 54 modern humans from Russia, the mtDNA of 6 Neanderthals, and the mtDNA of 1 chimpanzee and 1 bonobo.

Neanderthal may have bred with Denisovians

(The sex of X-woman was unidentified; the name X-woman comes from the fact that mitochondrial DNA passes only through the female line.)

X-woman's mtDNA was differed from the mtDNA of modern and Neanderthals, showing that she belonged to a separate species.

This was the first time that DNA sequencing - rather than the structure of fossils - was used to describe a hominid. (Hominids include humans, chimpanzees, bonobos, orangutans and gorillas.)

A Denisovan tooth and toe bone, also from Denisova Cave, were identified later.

There is evidence that Denisovans, Neanderthals and modern humans all lived in this cave.

We now know that at least four different species of human beings - Homo sapiens (modern humans), Homo neanderthalensis (Neanderthals), Homo floresiensis, and Denisovans- have lived in Europe and Asia.

Later on, researchers were able to sequence the full Denisovan genome from nuclear DNA.

They found that modern humans and Denisovans diverged between 170,000 and 700,000 years ago.

Modern humans from Melanesia and aborigines from the Philippines and Australia have some Denisovan DNA.  About 6 percent of the genes of Papuans are Denisovan.

Scientist think that Denisovans and modern humans might have met and interbred in central Asia; the humans might then traveled onward to islands in Oceania, where they settled.

Modern humans from central Asia today do not have traces of Denisovan DNA.