(CNN) -- An overlooked female pinkie bone put in storage after it was discovered in a Siberian cave two years ago points to the existence of a previously unknown prehistoric human species, anthropologists say.

And the lineage of that species may survive today in some people in Papua New Guinea and nearby islands, scientists say.

A report on the discovery of the finger was published in the December 23 edition of the scientific journal Nature.

Anthropologists say the 30,000- to 50,000-year-old finger is evidence of a new population of hominids they call Denisovans. The name is derived from the southern Siberian cave in which the finger bone was found.

Geneticists say the finger probably belonged to a 6- or 7-year-old girl.

"The whole story is incredible. It's like a surprising Christmas present," said Carles Lalueza Fox, a Spanish paleontologist not involved in the research who was quoted in the online article.

The 3 billion-letter nuclear genome derived from the child's finger shows that the ice-age population of early humans was more diverse than previously thought. Also, a comparison of the genome to modern humans indicates that Melanesian inhabitants of Papua New Guinea and various South Pacific islands inherited as much as 5 percent of their DNA from Denisovans.

The genome research was conducted at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

The Denisovans, the scientists say, were more closely related to Neanderthals than modern humans. The discovery in Siberia suggests they may have lived across a wide swath of Asia and are likely to have intermingled with the ancestors of modern humans who migrated eastward from Africa.