A mysterious new species of human being who lived alongside our ancestors 30,000 years ago has been discovered by scientists.

The cavemen, called Denisovans, were identified from DNA taken from a tooth and finger bone found in a cave in Siberia.

They walked the Earth during the last Ice Age when modern humans were developing sophisticated stone tools, jewellery and art.

The finding means there were at least three distinct members of the human family tree alive at the time - modern humans, Denisovans and Neanderthals.

The bone belonged to a young girl nicknamed the X-Woman.

Provisional tests published earlier this year suggested she belonged to an entirely new species. Now a fully DNA analysis has confirmed her place on the increasingly muddled human family tree.

The discovery follows the controversial discovery of another 'new' species of 3 ft tall human called the Hobbit on an Indonesian island in 2004.

However, many researchers have dismissed the Hobbit, claiming the bones came from a modern human with a growth disorder.

The little finger belonged to a girl aged around five to seven and was found in the Denisova cave in the Altai Mountains in southern Siberia in 2008 alongside ornaments and jewellery.

The Denisovans were physically different from the thickset Neanderthals and modern humans although they also walked upright two legs.

The tooth resembles much older human ancestors - such as Homo erectus - which died out one million years ago. The Denisovans lived at a time when our ancestors, and the Neanderthals, were fishing and hunting, wearing jewellery, painting caves and making animal carvings.

The DNA test show that the tooth and finger bone came from different people, the researchers report in the journal Nature.

It is only in the last decade that scientists have been able to retrieve DNA from fossils. Before that they could only identify bones from their shape and size.

The study found extracts of Denisovan DNA in modern day inhabitants of Melanesia - the islands to the north and east of Australia which include New Guinea. That suggests the Denisovans interbred with the ancestors of Melanesians and may have been widespread in Asia.