Wednesday, November 02, 2011 7:51:51 PM
Genes of Extinct Ancestor Survive in Modern Humans
Global map of Denisovan gene frequency in modern human genomes.
(Jacobsson and Skoglund/Proceedings of the National Academy of Sciences)
By Brandon Keim
October 31, 2011
Genes inherited from long-extinct human ancestors may be more common than thought, suggesting a Homo sapiens origin story with more than a few evolutionary one-night stands.
The latest findings involve genes from Denisovans, a recently-discovered member of the Homo genus [ http://www.wired.com/wiredscience/2010/12/denisovans/ ] who lived in central and eastern Asia until 40,000 years ago. Denisovans, humans and neanderthals last shared a common ancestor about 1 million years ago.
Earlier research found lingering Denisovan traces in genomes of people from Oceania [ http://www.newscientist.com/article/mg21128323.200-the-vast-asian-realm-of-the-lost-humans.html ]. Now they’ve been found in southeast Asia, too.
“We haven’t been a very exclusive species, with a very narrow origin,” said Martin Jacobsson. Interbreeding with other members of the human family tree “is not a unique event. It’s a more complex story than we thought before.”
In a study [ http://www.pnas.org/content/early/2011/10/24/1108181108 ] published Oct. 31 in the Proceedings of the National Academy of Sciences, Jacobsson and co-author Pontus Skoglund searched through 1,500 human genome scans from around the world for genes found in Denisovans but not chimpanzees or Neanderthals.
While the previous finding of Denisovan inheritance involved analysis of ultra-high-resolution human genome scans, of which only a few exist, Jacobsson used low-resolution scans. These are more commonly available and allowed the researchers to detect Denisovan signals in genomes from mainland southeast Asia. A signal also appeared in South America, but Jacobsson said that’s probably a false positive.
The 40,000 year-old tooth from which Denisovans were first identified in 2010.
David Reich et al./Nature
Beyond the fun of knowing that Denisovan genomes live on, the findings add to a growing sense of the richness of the human evolutionary story.
Until relatively recently, it was thought that human ancestors trekked out of Africa about 100,000 years ago in a single straight shot, descending without diversion into modernity. But what’s emerged from fossil findings in recent years is a picture of Homo sapiens and its near relatives flowing out of Africa again and again, with some populations vanishing and others surviving, often living side-by-side.
Now, thanks to well-preserved ancient genomes, it’s possible to look at mixing: Evidence of interbreeding with Neanderthals [ http://www.wired.com/wiredscience/2010/05/neanderthal-genome/ ] in northern Europe was found, followed by the Denisovan studies. Critically, the new findings fit a genetic pattern suggesting multiple episodes of interbreeding with Denisovans.
“We were evolving for a little while, then isolated, then mixed again,” said Jacobsson. “It’s not so simple that you can say, there’s only been one admixture.”
“I find it really cool that people use the archaic genomes we produced to try to arrive at new insights,” said geneticist Svante Paabo of Germany’s Max Planck Institute, who originally sequenced the Denisovan genome from 40,000-year-old fingerbones found in a Siberian cave [ http://www.wired.com/wiredscience/2010/12/denisovans/ ]. “Of course one will have to see which of them hold up.”
As for what Denisovan genes do for people who have them, it’s hard to say. Unlike Neanderthal genes, which seem to have given human immune systems a boost [ http://www.livescience.com/15754-neanderthals-immunity-boost-humans.html ], Denisovan gene function isn’t yet understood.
“It might take a little longer, until we get better-quality ancient genomes,” said Jacobsson. “But I’m guessing there are people out there trying to do this now.”
Citation: “Archaic human ancestry in East Asia.” By Pontus Skoglund and Mattias Jakobsson. Proceedings of the National Academy of Sciences, Vol. 108 No. 44, Oct. 31, 2011.
See Also:
Neanderthals Mated With Humans Outside of Africa
http://www.wired.com/wiredscience/2011/07/neanderthal-human-mating/
Neanderthals Had Feelings, Too
http://www.wired.com/wiredscience/2010/10/neanderthal-feelings/
Wired.com © 2010 Condé Nast Digital
http://www.wired.com/wiredscience/2011/10/denisovan-genes/ [with comments]
===
Fossil Teeth Put Humans in Europe Earlier Than Thought
By JOHN NOBLE WILFORD
Published: November 2, 2011
The fossils seemed hardly worth a second look. The one from England was only a piece of jawbone with three teeth, and the other, from southern Italy, was nothing more than two infant teeth. But scientists went ahead, re-examining them with refined techniques, and found that one specimen’s age had previously been significantly underestimated and that the other’s dating and identity had been misinterpreted.
They had in fact discovered the oldest known skeletal remains of anatomically modern humans in the whole of Europe, two international research teams reported Wednesday.
The scientists who made the discovery and others who study human origins say they expect the findings to reignite debate over the relative capabilities of the immigrant modern humans and the indigenous Neanderthals, their closest hominid relatives; the extent of their interactions; and perhaps the reasons behind the Neanderthal extinction. The findings have already prompted speculation that the Homo sapiens migrations into Europe may have come in at least two separate waves, rather than just one.
In tests conducted at the Oxford Radiocarbon Accelerator Unit in England, the baby teeth from Italy were dated at 43,000 to 45,000 years old. Other analysis showed the teeth to be those of a modern human, not a Neanderthal, as previously thought when the fossil was unearthed in 1964 from the Grotta del Cavallo.
Similar tests at Oxford established that the age of the jawbone, from Kents Cavern near Torquay, Devon, had been significantly underestimated, by about 7,000 years, probably because of contamination when it was originally dated in 1989. The age is now set at 41,500 to 44,200 years old, making this the oldest known modern human fossil from northwestern Europe.
These dates are remarkable on several counts, scientists said. The earliest reliably dated European modern human specimen, up to now, came from the Pestera cu Oase site in Romania, a long way east from the English coast. The Romanian fossil’s age is estimated at 37,800 to 42,000 years old. No stone tools or other artifacts were found with it.
And in the absence of early fossils, archaeologists had not been sure who made some of the stone tools they were uncovering, the arriving humans or the Neanderthals. It had been generally assumed that modern humans probably entered Europe at least as early as 45,000 years ago, based on changing patterns of artifacts that soon followed.
The two papers describing the new research were published Wednesday by the journal Nature. The lead author of the jawbone report [ http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10484.html ] was Thomas Higham of the University of Oxford. The principal author of the report on the baby teeth [ http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10617.html ] from Cavallo was Stefano Benazzi of the University of Vienna.
Not only does the jawbone indicate “the wide and rapid dispersal of the earliest moderns across Europe” during the last ice age, more than 40,000 years ago, Dr. Higham’s team wrote, it was also found in cave layers associated with a technology that archaeologists call the Aurignacian culture. The scientists said this “fills a key gap” between the earliest human skeletal remains and the earliest dated stone and bone Aurignacian tools and weapons.
Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis and an author of the Higham paper, said the artifacts associated with the Kents Cavern fossil “confirms what researchers have long suspected, that the human newcomers spread the Aurignacian culture.”
In a statement issued by Oxford, Dr. Higham also pointed out that the earlier dates for these fossils meant “that early humans must have coexisted with Neanderthals in this part of the world, something which a number of researchers have doubted.”
The confirmed early appearance of modern humans in Europe gave them more time for contacts with Neanderthals before the latter’s extinction about 30,000 years ago. Although recent genetic research shows some evidence of interbreeding between the species, there was uncertainty as to how much contact the two had in Europe, as opposed to earlier interactions in western Asia. It is still not clear how widespread was the Neanderthal population in their final millenniums; after a steady decline, the last of them seemed to disappear in their cul-de-sac of a refuge in southern Iberia.
Determining the age for any samples more than 40,000 years old was no sure thing. At that age, levels of remaining radiocarbon are low, and contamination can be a serious problem. As an alternative, Katerina Douka of Oxford, a member of the team examining the Italian specimen, focused on the dating of marine shell beads found in the same archaeological levels as the teeth, a technique that has proven successful at other sites in Europe.
When the teeth had been classified as Neanderthal, it was assumed that artifacts in the Cavallo site — bone tools and ornaments in a style known as the Uluzzian culture — were also considered Neanderthal creations. Now archaeologists suspect that they should be attributed to modern humans.
Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York who was not involved in the research, said, “The tendency right now is to downplay associating Neanderthals with any cultural developments after humans got to Europe.”
Chris Stringer and Tim Compton, both of the Natural History Museum, London, and members of the Higham group, obtained radiocarbon dates of animal bones found close to the jawbone in Kents Cavern and used a statistical modeling method to calculate the age of the human fossil. They further used CT scans to produce 3-D models of the worn teeth and thus confirm that the fossil was indeed from a human, not a Neanderthal.
“Everybody is going to wish some of that evidence was better,” Dr. Tattersall said. “It is pretty slender, but I have no reason to dispute it.”
Dr. Stringer elaborated in an e-mail on some possible implications of the two discoveries. Perhaps some of the “transitional cultures” that preceded the Aurignacian, he said, were introduced by “multiple early waves of modern humans coming into Europe.” For example, the Kents Cavern fossil might represent an early dispersal through central Europe that crossed into Britain on a land bridge where the North Sea is now. The Cavallo remains might represent a possibly even earlier migration along the southern European coasts.
Richard G. Klein, an archaeologist at Stanford University, said he was “really impressed” by the new findings. Hearing of Dr. Stringer’s idea, Dr. Klein joined in the spirit of conjecture, noting that Homo sapiens was on the move at that time, venturing as far as Australia by about 45,000 years ago.
© 2011 The New York Times Company
http://www.nytimes.com/2011/11/03/science/fossil-teeth-put-humans-in-europe-earlier-than-thought.html [ http://www.nytimes.com/2011/11/03/science/fossil-teeth-put-humans-in-europe-earlier-than-thought.html?_r=1&pagewanted=all ]
Global map of Denisovan gene frequency in modern human genomes.
(Jacobsson and Skoglund/Proceedings of the National Academy of Sciences)
By Brandon Keim
October 31, 2011
Genes inherited from long-extinct human ancestors may be more common than thought, suggesting a Homo sapiens origin story with more than a few evolutionary one-night stands.
The latest findings involve genes from Denisovans, a recently-discovered member of the Homo genus [ http://www.wired.com/wiredscience/2010/12/denisovans/ ] who lived in central and eastern Asia until 40,000 years ago. Denisovans, humans and neanderthals last shared a common ancestor about 1 million years ago.
Earlier research found lingering Denisovan traces in genomes of people from Oceania [ http://www.newscientist.com/article/mg21128323.200-the-vast-asian-realm-of-the-lost-humans.html ]. Now they’ve been found in southeast Asia, too.
“We haven’t been a very exclusive species, with a very narrow origin,” said Martin Jacobsson. Interbreeding with other members of the human family tree “is not a unique event. It’s a more complex story than we thought before.”
In a study [ http://www.pnas.org/content/early/2011/10/24/1108181108 ] published Oct. 31 in the Proceedings of the National Academy of Sciences, Jacobsson and co-author Pontus Skoglund searched through 1,500 human genome scans from around the world for genes found in Denisovans but not chimpanzees or Neanderthals.
While the previous finding of Denisovan inheritance involved analysis of ultra-high-resolution human genome scans, of which only a few exist, Jacobsson used low-resolution scans. These are more commonly available and allowed the researchers to detect Denisovan signals in genomes from mainland southeast Asia. A signal also appeared in South America, but Jacobsson said that’s probably a false positive.
The 40,000 year-old tooth from which Denisovans were first identified in 2010.
David Reich et al./Nature
Beyond the fun of knowing that Denisovan genomes live on, the findings add to a growing sense of the richness of the human evolutionary story.
Until relatively recently, it was thought that human ancestors trekked out of Africa about 100,000 years ago in a single straight shot, descending without diversion into modernity. But what’s emerged from fossil findings in recent years is a picture of Homo sapiens and its near relatives flowing out of Africa again and again, with some populations vanishing and others surviving, often living side-by-side.
Now, thanks to well-preserved ancient genomes, it’s possible to look at mixing: Evidence of interbreeding with Neanderthals [ http://www.wired.com/wiredscience/2010/05/neanderthal-genome/ ] in northern Europe was found, followed by the Denisovan studies. Critically, the new findings fit a genetic pattern suggesting multiple episodes of interbreeding with Denisovans.
“We were evolving for a little while, then isolated, then mixed again,” said Jacobsson. “It’s not so simple that you can say, there’s only been one admixture.”
“I find it really cool that people use the archaic genomes we produced to try to arrive at new insights,” said geneticist Svante Paabo of Germany’s Max Planck Institute, who originally sequenced the Denisovan genome from 40,000-year-old fingerbones found in a Siberian cave [ http://www.wired.com/wiredscience/2010/12/denisovans/ ]. “Of course one will have to see which of them hold up.”
As for what Denisovan genes do for people who have them, it’s hard to say. Unlike Neanderthal genes, which seem to have given human immune systems a boost [ http://www.livescience.com/15754-neanderthals-immunity-boost-humans.html ], Denisovan gene function isn’t yet understood.
“It might take a little longer, until we get better-quality ancient genomes,” said Jacobsson. “But I’m guessing there are people out there trying to do this now.”
Citation: “Archaic human ancestry in East Asia.” By Pontus Skoglund and Mattias Jakobsson. Proceedings of the National Academy of Sciences, Vol. 108 No. 44, Oct. 31, 2011.
See Also:
Neanderthals Mated With Humans Outside of Africa
http://www.wired.com/wiredscience/2011/07/neanderthal-human-mating/
Neanderthals Had Feelings, Too
http://www.wired.com/wiredscience/2010/10/neanderthal-feelings/
Wired.com © 2010 Condé Nast Digital
http://www.wired.com/wiredscience/2011/10/denisovan-genes/ [with comments]
===
Fossil Teeth Put Humans in Europe Earlier Than Thought
By JOHN NOBLE WILFORD
Published: November 2, 2011
The fossils seemed hardly worth a second look. The one from England was only a piece of jawbone with three teeth, and the other, from southern Italy, was nothing more than two infant teeth. But scientists went ahead, re-examining them with refined techniques, and found that one specimen’s age had previously been significantly underestimated and that the other’s dating and identity had been misinterpreted.
They had in fact discovered the oldest known skeletal remains of anatomically modern humans in the whole of Europe, two international research teams reported Wednesday.
The scientists who made the discovery and others who study human origins say they expect the findings to reignite debate over the relative capabilities of the immigrant modern humans and the indigenous Neanderthals, their closest hominid relatives; the extent of their interactions; and perhaps the reasons behind the Neanderthal extinction. The findings have already prompted speculation that the Homo sapiens migrations into Europe may have come in at least two separate waves, rather than just one.
In tests conducted at the Oxford Radiocarbon Accelerator Unit in England, the baby teeth from Italy were dated at 43,000 to 45,000 years old. Other analysis showed the teeth to be those of a modern human, not a Neanderthal, as previously thought when the fossil was unearthed in 1964 from the Grotta del Cavallo.
Similar tests at Oxford established that the age of the jawbone, from Kents Cavern near Torquay, Devon, had been significantly underestimated, by about 7,000 years, probably because of contamination when it was originally dated in 1989. The age is now set at 41,500 to 44,200 years old, making this the oldest known modern human fossil from northwestern Europe.
These dates are remarkable on several counts, scientists said. The earliest reliably dated European modern human specimen, up to now, came from the Pestera cu Oase site in Romania, a long way east from the English coast. The Romanian fossil’s age is estimated at 37,800 to 42,000 years old. No stone tools or other artifacts were found with it.
And in the absence of early fossils, archaeologists had not been sure who made some of the stone tools they were uncovering, the arriving humans or the Neanderthals. It had been generally assumed that modern humans probably entered Europe at least as early as 45,000 years ago, based on changing patterns of artifacts that soon followed.
The two papers describing the new research were published Wednesday by the journal Nature. The lead author of the jawbone report [ http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10484.html ] was Thomas Higham of the University of Oxford. The principal author of the report on the baby teeth [ http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10617.html ] from Cavallo was Stefano Benazzi of the University of Vienna.
Not only does the jawbone indicate “the wide and rapid dispersal of the earliest moderns across Europe” during the last ice age, more than 40,000 years ago, Dr. Higham’s team wrote, it was also found in cave layers associated with a technology that archaeologists call the Aurignacian culture. The scientists said this “fills a key gap” between the earliest human skeletal remains and the earliest dated stone and bone Aurignacian tools and weapons.
Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis and an author of the Higham paper, said the artifacts associated with the Kents Cavern fossil “confirms what researchers have long suspected, that the human newcomers spread the Aurignacian culture.”
In a statement issued by Oxford, Dr. Higham also pointed out that the earlier dates for these fossils meant “that early humans must have coexisted with Neanderthals in this part of the world, something which a number of researchers have doubted.”
The confirmed early appearance of modern humans in Europe gave them more time for contacts with Neanderthals before the latter’s extinction about 30,000 years ago. Although recent genetic research shows some evidence of interbreeding between the species, there was uncertainty as to how much contact the two had in Europe, as opposed to earlier interactions in western Asia. It is still not clear how widespread was the Neanderthal population in their final millenniums; after a steady decline, the last of them seemed to disappear in their cul-de-sac of a refuge in southern Iberia.
Determining the age for any samples more than 40,000 years old was no sure thing. At that age, levels of remaining radiocarbon are low, and contamination can be a serious problem. As an alternative, Katerina Douka of Oxford, a member of the team examining the Italian specimen, focused on the dating of marine shell beads found in the same archaeological levels as the teeth, a technique that has proven successful at other sites in Europe.
When the teeth had been classified as Neanderthal, it was assumed that artifacts in the Cavallo site — bone tools and ornaments in a style known as the Uluzzian culture — were also considered Neanderthal creations. Now archaeologists suspect that they should be attributed to modern humans.
Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York who was not involved in the research, said, “The tendency right now is to downplay associating Neanderthals with any cultural developments after humans got to Europe.”
Chris Stringer and Tim Compton, both of the Natural History Museum, London, and members of the Higham group, obtained radiocarbon dates of animal bones found close to the jawbone in Kents Cavern and used a statistical modeling method to calculate the age of the human fossil. They further used CT scans to produce 3-D models of the worn teeth and thus confirm that the fossil was indeed from a human, not a Neanderthal.
“Everybody is going to wish some of that evidence was better,” Dr. Tattersall said. “It is pretty slender, but I have no reason to dispute it.”
Dr. Stringer elaborated in an e-mail on some possible implications of the two discoveries. Perhaps some of the “transitional cultures” that preceded the Aurignacian, he said, were introduced by “multiple early waves of modern humans coming into Europe.” For example, the Kents Cavern fossil might represent an early dispersal through central Europe that crossed into Britain on a land bridge where the North Sea is now. The Cavallo remains might represent a possibly even earlier migration along the southern European coasts.
Richard G. Klein, an archaeologist at Stanford University, said he was “really impressed” by the new findings. Hearing of Dr. Stringer’s idea, Dr. Klein joined in the spirit of conjecture, noting that Homo sapiens was on the move at that time, venturing as far as Australia by about 45,000 years ago.
© 2011 The New York Times Company
http://www.nytimes.com/2011/11/03/science/fossil-teeth-put-humans-in-europe-earlier-than-thought.html [ http://www.nytimes.com/2011/11/03/science/fossil-teeth-put-humans-in-europe-earlier-than-thought.html?_r=1&pagewanted=all ]
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