8/9/2019 DNA From Bone Shows New Human Forerunner, And Raises Array of Questions

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from bone shows new human forerunner, and raises array of questions

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DNA from bone shows new human forerunner, andaises array of questions

David Brownursday, March 25, 2010; A01

team of European researchers has identified a new lineage of proto-human that leftfrica about a million years ago, traveling as far as Siberia and then dying out -- ascovery that raises new questions about early human history.

he existence of the new lineage was discovered by analyzing DNA extracted from angle bone fragment, according to a study published Wednesday in the journalature. What the beings looked like, how they lived and what happened to them are aystery. All that's known is that they existed as recently as 40,000 years ago, which ise approximate age of the bone.

Whoever carried this DNA out of Africa is some new creature that hasn't been on ourdar screen so far," said Johannes Krause, a researcher at the Max Planck Institute for Evolutionary Anthropology in Germany, wh

elped lead the research team.

he new lineage, which has not yet been declared a separate species, occupied Russia's Altai Mountains during a long period whenarly modern humans and Neanderthals were also there. Whether its members had contact with those other early people -- or migave interbred with them -- isn't known.

evertheless, the possible cohabitation of the three groups gives rise to at least two narratives of the first chapter of Eurasian histo

hat landmass might have been a peaceable kingdom of competing "hominin" species. Or it could have been the site of genocide, e Neanderthals and the just-discovered group of beings dying out to the last man and woman.

People are going to be what we call 'gobsmacked' by this news," said Terry Brown, a molecular paleontologist at the University ofanchester, who wrote a commentary accompanying the paper in Nature. "There is going to be open-mouth amazement."

part from adding an unknown prehistoric cousin and a new "out-of-Africa" migration to the story of our origins, the finding marks rst in the way anthropological discoveries are made. The new lineage was determined to be distinct from other early humans not e shape and size of its skeleton, but exclusively by differences in its genetic material.

hat material was extracted from a fragment of a child's pinkie in the form of mitochondrial DNA. The bone, found in 2008 in a cavuring a routine archeological excavation, is the only physical remains of the group. As a consequence, the researchers have no ideahat its members looked like compared with the more ancient Homo erectus, the beetle-browed Neanderthals or the recentlyscovered "Hobbit people" of Indonesia.

he discovery raises the possibility that there might have been many waves of migration out of Africa by evolving proto-humans, earoup genetically distinguishable from the others. It is likely to spur the search for other prehistoric bone fragments in places cool ary enough to have surviving remnants of DNA.

Maybe it is overly simplistic to think of particular migrations out of Africa," said Svante Paabo, the other leader of the German teamThere might have been a more or less continuous flow of migration. The picture that may emerge in the next few years is likely touch more complicated."

he vast majority of the DNA in human cells resides in the nucleus, in long strands called chromosomes. The chromosomes encodebout 20,000 genes, which one inherits from both mother and father.

tiny amount of DNA, however, is in satellite structures outside the nucleus called mitochondria. They are inherited exclusively fromother. Mitochondrial DNA, or mtDNA, which encodes fewer than 40 genes, defines an unbroken line of mother-to-child descent.

he linear order (called the "sequence") of the DNA "letters" in mtDNA is extremely stable over time. Nevertheless, mutations do cr, and the rate at which they do is known, at least approximately. For that reason, differences in mtDNA function as a "molecularock." They can be used to estimate how long ago the two populations had an ancestor in common.

odern humans differ from Neanderthals by an average of 202 "letters" out of about 16,500 in the complete mtDNA strand. Theberian bone's mtDNA differs by 385 letters. Chimpanzees and modern humans differ by 1,462 mtDNA letters, on average. Analysiose differences led the researchers to conclude that the new lineage shared a common ancestor with Neanderthals and modern

umans about 1 million years ago.

more ancient proto-human, Homo erectus, left Africa about 1.9 million years ago. Neanderthals' ancestors left 500,000 to 300,00ears ago. Modern humans left 50,000 years ago.

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8/9/2019 DNA From Bone Shows New Human Forerunner, And Raises Array of Questions

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from bone shows new human forerunner, and raises array of questions

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he researchers think the ancestors of the "Denisova hominin" -- named after the cave where the finger bone was found -- almostertainly left Africa in a migration separate from those of the other species. Paabo believes it probably occurred 800,000 to 900,000ears ago.

he bone fragment has also yielded remnants of nuclear DNA, which may be enough to sketch a few details of its owner, believed te a 6- or 7-year-old child.

the nuclear DNA's genetic fingerprint is similar to that of modern humans or Neanderthals, it will imply that some of the child'sncestors were the product of interbreeding with those species. On the other hand, if it is as different from those species' as theitochondrial DNA is, the researchers can conclude the child was a "purebred" member of the newly discovered lineage.

o far, there's no firm evidence of interbreeding between early modern humans and Neanderthals. To discover that the Denisovaominin was a hybrid -- the answer should be known in a few months -- would change the view of man's prehistory considerably.

eanderthal remains have been found less than 100 miles from Denisova Cave. Artifacts in nearby caves and in Denisova itself sugge presence of Upper Palaeolithic-age people, which might include modern humans. The time when the three groups occupied the

ame region spanned at least 10,000 years; whether they were exact contemporaries is unknown.

they were, Paabo said, that "raises the potential of all sorts of interactions" between them. One is a fight to the death -- althoughere's no evidence for that so far.

Something happened that only we survived," Paabo said. He added that he shares the view that "we were somehow responsible" e disappearance of the other lineages. "But whether it was in a direct way, or some kind of ecological competition, we don't know

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