New human group
Via TYD, this report in the NY Times by Nicholas Wade:
A previously unknown kind of human group vanished from the world so completely that it has left behind the merest wisp of evidence that it ever existed — a single bone from the little finger of a child, buried in a cave in the Altai mountains of southern Siberia.
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 researchers, led by Johannes Krause and Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, are careful not to call the Denisova child a new human species, though it may prove to be so, because the evidence is preliminary.
But they say the genetic material extracted from the bone, an element called mitochondrial DNA, belonged to a distinct human lineage that migrated out of Africa at a different time from the two known archaic human species. Homo erectus, found in East Asia, left Africa two million years ago, and the ancestor of Neanderthals emigrated some 500,000 years ago. The number of differences found in the child’s DNA indicate that its ancestors left Africa about one million years ago, the researchers say. Their report is published online in the journal Nature.
Dr. Paabo, a pioneer in decoding ancient human DNA, said at a news conference that before asserting that the Denisova child was a new species, he needed to rule out the possibility that it belonged to a population formed by interbreeding between the new lineage and a known species. He said he was analyzing the rest of the child’s DNA, from the main or nuclear genome, to test this possibility.
“Back at the time this lineage came out of Africa, it had to have been a distinct group, perhaps a distinct species,” he said. “But whether or not this individual was a distinct species, we have to wait for the nuclear DNA.”
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…
Continue reading. It makes one wonder how many other near-human species vanished without a trace.
