This undated photo provided by the journal Nature shows a view from a rock above Denisova cave to the excavation field camp in in Altai Mountains of southern Siberia. AP
Scientists have decoded genetic material from an unidentified human ancestor that lived in Siberia and concluded it might be a new member of the human family tree
New strain of humankind identified
New York — — The Associated Press Published on Wednesday, Mar. 24, 2010 2:18PM EDT Last updated on Wednesday, Mar. 24, 2010 2:19PM EDT
In the latest use of DNA to investigate the story of humankind, scientists have decoded genetic material from an unidentified human ancestor that lived in Siberia and concluded it might be a new member of the human family tree.
The DNA doesn’t match modern humans or Neanderthals, two species that lived in that area around the same time — 30,000 to 50,000 years ago.
Instead, it suggests the Siberian species lineage split off from the branch leading to moderns and Neanderthals a million years ago, the researchers calculated. And they said that doesn’t seem to match the history of human ancestors previously known from fossils.
So the Siberian species may be brand new, although the scientists cautioned that they’re not ready to make that claim yet.
Other experts agreed that while the Siberian species may be new, the case is far from proven.
“We really don’t know,” said Ian Tattersall of the American Museum of Natural History in New York, who wasn’t involved in the new research.
But “the human family tree has got a lot of branchings. It’s entirely plausible there are a lot of branches out there we don’t know about.”
The discovery “is like many new finds,” said Eric Delson of Lehman College of the City University of New York, who didn’t participate in the new work. “You say, `I think this is different, but I’m not sure.’ And then you look for more material and you try to make better comparisons.”
The researchers, who say the Siberian species is not a direct ancestor of modern-day people, hope further genetic analysis will show if it’s a new species. Some experts are skeptical about whether such analysis will resolve that.
In any case, the finding emphasizes that quite unlike the present day, anatomically modern humans have often lived alongside their evolutionary relatives, one expert said.
“We weren’t alone,” said Todd Disotell of New York University, who was familiar with the new work. “When we became modern, we didn’t instantly replace everybody. There were other guys running around who survived quite well until very, very recently.”
Just last month, other researchers used DNA analysis to show the genetic diversity still present in residents of Africa, the cradle of the human race. And another project produced the first genome of an ancient human — a man who lived in Greenland some 4,000 years ago.
The new work, published online Wednesday by the journal Nature, is reported by Johannes Krause and Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and others.
They describe mapping DNA from what appeared to be a youngster’s pinkie finger bone, which had been recovered in 2008 from Denisova Cave in Altai Mountains of southern Siberia. They showed how it differed from DNA of 54 modern-day people and six Neanderthals.
Their analysis indicated the Siberian species last shared a common ancestor with modern humans and Neanderthals about 1 million years ago. That in turn suggested there was a previously unrecognized migration out of Africa around that time, they said.
The work decoded the complete set of DNA from mitochondria, the power plants of cells. That’s different from the better-known DNA that comes from cell nuclei and determines things like eye color. Mr. Paabo said the researchers are working to decode nuclear DNA from the Siberian species. That will reveal whether it was closely related to Neanderthals or today’s humans, and answer questions like whether it interbred with Neanderthals or ancestors of modern-day people, he said.
Without a completed analysis of the nuclear DNA, “we are not saying this is a new species,” Mr. Paabo said, although he said that’s a likely possibility.
Rick Potts, director of the Smithsonian Institution’s Human Origins Program, said the Siberian find might represent Homo heidelbergensis or Homo erectus. And even analysis of the Siberian species’ nuclear DNA won’t show if it’s distinct from those ancestors, he said.
As for the study’s suggestion of a migration out of Africa about a million years ago, Mr. Potts said there’s already evidence of one or two migrations around that time.
The finger bone recovered from the Siberian species is not enough for a fossil-to-fossil comparison with other ancient species to show whether it’s a new species, Mr. Delson said.
He suspects it might be a descendant of Homo erectus that’s already documented in some fossil remains in northern Africa and Europe. Scientists are still trying to figure out how many species of the Homo grouping those bones represent and what name or names to attach to them, he said.
Mr. Disotell said the new creature could be an early version of Homo antecessor, a forerunner of Neanderthals and modern humans known from fossils in Spain. Or, he said, it could be a new species. In fact, the eventual decision could hinge mostly on the philosophical question of just how different a creature has to be to be declared a new species, he said.
Mr. Potts said that in the new work, “what we’re seeing is a really, really interesting distant echo of the DNA history of human evolution…. This is an amazingly powerful technique that these guys have. This is going to be a growth industry in the study of human evolution.”
New human species found in Siberia
Human relative, identified from fragments of a finger bone, lived until as recently as 30,000 years ago, say scientists
Ian Sample, Science correspondent
guardian.co.uk, Wednesday 24 March 2010 18.00 GMT
The remains of a little finger discovered in a cave in the mountains of southern Siberia belong to a previously unknown human ancestor, scientists said today.
The finding suggests an undocumented human species lived alongside Neanderthals and early modern humans in parts of Asia as recently as 30,000 years ago. If confirmed, it would be the first time a new human ancestor has been identified since the discovery of Homo floresiensis, the diminutive “hobbits” that lived on the Indonesian island of Flores until 13,000 years ago.
Fragments of the finger bone were recovered from Denisova cave in the Altai mountain range that straddles Russia, Mongolia, China and Kazakhstan. The cave was occupied by humans for 125,000 years and a variety of stone tools and bones have been recovered.
The size of the bone has led scientists to believe it came from a child, aged between five and seven, though they are unable to say whether it was male or female.
Scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, ran genetic tests on the bone fragments and were stunned to find it did not match the DNA profile of Neanderthals or early modern humans.Johannes Krause sequenced DNA from mitochondria, the sub-cellular bodies that carry genetic material passed down only the maternal line. Because the DNA came from the mother, they called the creature “X-woman”.
“It really looked like something I had never seen before. It was a sequence which is similar in some ways to humans, but still quite distinct,” Krause said. It is the first time a new type of human has been identified from DNA alone.
By comparing the DNA with sequences from Neanderthals and modern humans, Krause’s team concluded that modern humans shared a common ancestor with the creature a million years ago. Humans and Neanderthals diverged from an ancestor that lived 500,000 years ago.
When Krause saw the results of the genetic test, he called project leader Svante Pääbo. “It was absolutely amazing, I didn’t believe him. I thought he was pulling my leg,” Pääbo said. The bone fragments were recovered from a layer of rock in the cave dated to between 48,000 and 30,000 years ago.
The first humans to move from Africa to Eurasia were Homo erectus 1.9m years ago, but scientists believed they died out around 100,000 years ago. The new species probably migrated from Africa more recently, around 1m years ago, and survived in Eurasia until at least 40,000 years ago.
Krause’s team is now analysing DNA from the nuclei of cells in the finger fragments in the hope of locating the species in the human family tree. The tests should also indicate whether there was any interbreeding between the new species, Neanderthals and modern humans.
“There were at least three different forms of humans in the area between 30,000 and 40,000 years ago, and there were also the hobbits in Indonesia, so the picture of what was around in human form in the late Pleistocene gets a lot more complex and a lot more interesting,” Pääbo said.
Chris Stringer, head of human origins at the Natural History Museum in London, said: “This new DNA work provides an entirely new way of looking at the still poorly understood evolution of humans in central and eastern Asia.”
guardian.co.uk © Guardian News and Media Limited 2010
Bone Yields Hints of Unknown Archaic Humans
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 on 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 in a news conference that before asserting 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 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.
The valley beneath the Denisova cave 30,000 years ago would have been mostly a steppe, or treeless grassland, according to pollen analysis, and it was roamed by ice-age species like the woolly mammoth and woolly rhino, Dr. Krause said.
The region was inhabited by both Neanderthals and modern humans at that time. Counting the new human lineage, three human species may have lived together in proximity. “So the picture of the humans around in the late Pleistocene gets a lot more complex and a lot more interesting,” Dr. Paabo said.
The standard view has long been that there were three human migrations out of Africa — those of Homo erectus; of the ancestor of Neanderthals; and finally, some 50,000 years ago, of modern humans. But in 2004, archaeologists reported that they had found the bones of miniature humans who lived on the Indonesian island of Flores until 13,000 years ago, posing a serious problem for this view. The new lineage is the second such challenge, and it suggests that human migrations out of Africa, though far from continuous, were more frequent than supposed.
“We are learning more and more what a luxuriant evolutionary tree humans have had,” said Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York. The tree during evolutionary time has kept sprouting new branches, all but one of which die off, before the process is repeated.
As little as 30,000 years ago, it now appears, there were five human species in the world: Homo erectus, the little Floresians, Neanderthals, modern humans and the new lineage from the Denisova cave. This is similar to the situation two million years ago, when four hominid species are known to have lived in the Turkana Basin of Kenya, Dr. Tattersall said.
“We think it’s normal to be alone in the world as we are today,” Dr. Tattersall said, and to see human evolution as a long trend leading to Homo sapiens. In fact, the tree has kept generating new branches that get cut off, presumably by the sole survivor. “The fossil record is very eloquent about this, and it’s telling us we are an insuperable competitor,” Dr. Tattersall said. Modern humans’ edge over other species probably emerged from their ability to process information: “We can invent alternatives in our heads instead of accepting nature as it is,” Dr. Tattersall said.
If the nuclear DNA of the Denisova child should differ as much as its mitochondrial DNA does from that of Neanderthals and modern humans, the case for declaring it a new species would be strengthened. But it would be unusual, if not unprecedented, for a new species to be recognized on the basis of DNA alone.
In new excavations starting this summer, archaeologists will look for remains more diagnostic than the finger bone. Researchers will also begin re-examining the fossil collections in museums to see if any wrongly assigned bones might belong instead to the species of the new lineage, Dr. Krause said.