Researchers extracted DNA from the bone and reported Wednesday that it differed conspicuously from that of both modern humans and of Neanderthals, the archaic human species that inhabited Europe until the arrival of modern humans on the continent some 44,000 years ago.
The child who carried the DNA lineage was probably 5 to 7 years old, but it is not yet known if it was a boy or a girl. The finger bone was excavated by Russian archaeologists in 2008 from a place known as the Denisova cave.
The finger bone was found in a layer laid down on the cave floor between 48,000 and 30,000 years ago, according to radiocarbon dating. At that time, toward the end of the Pleistocene Ice Age, which ended 10,000 years ago, the climate was probably much colder. The people of the new lineage presumably wore clothes, Dr. Krause said, because chimpanzees and gorillas cannot withstand much cold, suggesting that fur alone is inadequate protection.
The artifacts found in the cave in the same layer as the finger bone include ornaments and a bracelet that are typical of modern human sites from the Upper Paleolithic age in Europe. These are puzzling artifacts to be found with a nonmodern human species. But bones can move up and down in archaeological sites, and it is hard to know if the finger bone is truly associated with these artifacts, Dr. Krause said, even though there is little sign of mixing in the cave’s layers.