大約4萬5000至3萬年前，尼安德塔人(Neanderthal)和從非洲移居過來的現代人（智人,Homo Sapien）共存於歐亞大陸某些區域，但是現代人存活了下來，尼安德塔人卻消失了。幾年前國家地理頻道曾製作過專題加以探討，在台灣也不時重播。尼安德塔人是被消滅了？自然滅絕了？有沒有可能部分與智人融合了呢？
這一年來有幾個關於史前人類的研究與發現，五月的時候BBC刊載了一則報導，說是在現代人的基因中發現了部分尼安德塔人的基因。
前幾天又有新聞關於尼安德塔人的報導，是一種與尼安德塔人同時，的史前人類。命名為「丹尼索瓦」人（Denisovans），而且在現在的新幾內亞人身上發現約有4.8%的「丹尼索瓦人」的基因。
中國著名的北京猿人在二次大戰遺失，所以很難知道這北京猿人與智人間的關係。或許現在漢人身上也都有著部分北京猿人的基因呢！
尼安德塔人的東方遠親 考古學家在西伯利亞洞穴找到(2010/12/24 00:01)
記者鮑蓉蓉／編譯
考古學家去年在西伯利亞的丹尼索瓦洞穴（Denisova）當中挖掘出一塊史前人類的遺骨，因與現代人或尼安德塔人不同，屬於不同人種，起初被命名為「Ｘ女人」(X-Woman)，考古人員日前依洞穴名稱，將之命名為「丹尼索瓦」人（Denisovans），與尼安德塔人擁有一樣的祖先，為尼安德塔人的遠親。
尼安德塔人與丹尼索瓦人的祖先於約於50萬年前出現，並且都源自於非洲。
科學家單單從一顆智齒以及一塊手指碎骨當中，成功找出丹尼索瓦人的基因組合；證據顯示，丹尼索瓦人大約出現在40萬年前，從尼安德塔人的祖先當中分支出來。
尼安德塔人向西發展，隨後定居於歐洲與近東，丹尼索瓦人則是向東發展，約在4萬到5萬年前出沒在亞洲地區，隨之將他們的DNA「傳播」出去。22日刊登在「自然」期刊（Nature）的研究報告當中揭露，新幾內亞人的基因裡有4.8％屬於丹尼索瓦人。
研究人員為針對「混種」找出證據，將丹尼索瓦人的基因組合與來自南非、奈及利亞、中國大陸、法國以及新幾內亞的人類做比較，隨後發現丹尼索瓦人的基因最接近新幾內亞人。
新幾內亞位於澳洲以北，研究結果顯示，丹尼索瓦人的基因從西伯利亞橫跨至南亞，因此研究人員之一的帕布（Dr. Paabo）認為，丹尼索夫瓦屬於很成功的人種，但針對他們的外觀或是行為還是有所保留，並開玩笑道「你從我的基因組合也猜不出我長怎樣吧」。
考古學家所發現的尼安德塔人化石大約有2萬4千年至3萬年的歷史，出沒地帶為歐洲、近東以及俄羅斯，而尼安德塔人也有與不同人種混種的跡象。
研究人員根據DNA判斷，雖然尼安德塔人的祖先來自非洲，但他們2.5％的基因組合與當代歐洲人以及亞洲人較為類似，因此科學家推論，尼安德塔人自從5萬年前在非洲出現之後，在短時間內迅速地與不同人類的物種雜交混種。
考古學家早就認為，在人類進化過程中，有好幾種不同物種的人類互相混種，因此丹尼索瓦人的出現，替這個假設提供了一些資料，但研究人員同時也認為，需要找到更多證據來刻劃出人類的演進史。
December 22, 2010
Siberian Fossils Were Neanderthals’ Eastern Cousins, DNA Reveals
An international team of scientists has identified a previously shadowy human group known as the Denisovans as cousins to Neanderthals who lived in Asia from roughly 400,000 to 50,000 years ago and interbred with the ancestors of today’s inhabitants of New Guinea.
All the Denisovans have left behind are a broken finger bone and a wisdom tooth in a Siberian cave. But the scientists have succeeded inextracting the entire genome of the Denisovans from these scant remains. An analysis of this ancient DNA, published on Wednesday in Nature, reveals that the genomes of people from New Guinea contain 4.8 percent Denisovan DNA.
An earlier, incomplete analysis of Denisovan DNA had placed the group as more distant from both Neanderthals and humans. On the basis of the new findings, the scientists propose that the ancestors of Neanderthals and Denisovans emerged from Africa half a million years ago. The Neanderthals spread westward, settling in the Near East and Europe. The Denisovans headed east. Some 50,000 years ago, they interbred with humans expanding from Africa along the coast of South Asia, be queathing some of their DNA to them.
“It’s an incredibly exciting finding,” said Carlos Bustamante, a Stanford University geneticist who was not involved in the research.
The research was led by Svante Paabo, a geneticist at the Max PlanckInstitute for Evolutionary Anthropology in Liepzig, Germany. Dr. Paabo and his colleagues have pioneered methods for rescuing fragments of ancient DNA from fossils and stitching them together. In May, for example, they published a complete Neanderthal genome.
The stocky, barrel-chested Neanderthals left a fossil record stretching from about 240,000 to 30,000 years ago in Europe, the Near East and Russia. Analyzing the Neanderthal genome, Dr. Paabo and his colleagues concluded that humans and Neanderthals descended from common ancestors that lived 600,000 years ago.
But the scientists also found that 2.5 percent of the Neanderthal genome is more similar to the DNA of living Europeans and Asians thanto African DNA. From this evidence they concluded that Neanderthals interbred with humans soon after they emerged from Africa roughly50,000 years ago.
Dr. Paabo’s success with European Neanderthal fossils inspired him and his colleagues to look farther afield. They began to work with Anatoli Derevianko of the Russian Academy of Sciences, who explores Siberian caves in search of fossils of hominins (species more closely related to living humans than to chimpanzees, our closest living relatives).
Last year, Dr. Derevianko and his colleagues sent Dr. Paabo a nondescript fragment of a finger bone from a cave called Denisova. Dr.Derevianko thought that the fossil, which is at least 50,000 years old,might have belonged to one of the earliest humans to live in Siberia.
Dr. Paabo and his colleagues isolated a small bundle of DNA from thebone’s mitochondria, the energy-generating structures within our cells.Dr. Paabo and his colleagues were surprised to discover that theDenisova DNA was markedly different from that of either humans orNeanderthals. “It was a great shock to us that it was distinct fromthose groups,” Dr. Paabo said in an interview.
Dr. Paabo and his colleagues immediately set about to collect all theDNA in the Denisova finger bone. Once they had sequenced its genome,they sent the data to researchers at Harvard Medical School and theBroad Institute in Cambridge, Mass., to compare with other species.
The Massachusetts scientists concluded that the finger bone belonged toa hominin branch that split from the ancestors of Neanderthals roughly400,000 years ago. Dr. Paabo and his colleagues have named this lineagethe Denisovans.
Next, the researchers looked for evidence of interbreeding. Nick Patterson, a Broad Institute geneticist, compared the Denisovan genometo the complete genomes of five people, from South Africa, Nigeria,China, France and Papua New Guinea. To his astonishment, a sizable chunk of the Denisova genome resembled parts of the New Guinea DNA.
“The correct reaction when you get a surprising result is, ‘What am Idoing wrong?’ ” said Dr. Patterson. To see if the result was an error,he and his colleagues sequenced the genomes of seven more people,including another individual from New Guinea and one from theneighboring island of Bougainville. But even in the new analysis, theDenisovan DNA still turned up in the New Guinea and Bougainvillegenomes.
If the Denisovans did indeed have a range spreading from Siberia toSouth Asia, they must have been a remarkably successful kind of human.And yet, despite having the entire genome of a Denisovan, Dr. Paabocannot say much yet about what they were like. “By sequencing mycomplete genome, there’s very little you could predict about what Ilook like or how I behave,” he said.
One solid clue to what the Denisovans looked like emerged in January.Dr. Paabo and his team had flown to Novosibirsk to share their initialresults with Dr. Derevianko. Dr. Derevianko then presented them with awisdom tooth from Denisova.
Bence Viola, a paleoanthropologist in the Department of Human Evolutionat the Max Planck Institute of Evolutionary Anthropology, who was atthe meeting, was flummoxed. “I looked at it and said, ‘Ah, O.K., thisis not a modern human, and it’s definitely not a Neanderthal,”’ saidDr. Viola. “It was just so clear.”
The tooth had oddly bulging sides, for one thing, and for another, itslarge roots flared out to the sides. Back in Germany, Dr. Paabo and hiscolleagues managed to extract some mitochondrial DNA from the tooth. Itproved to be a nearly perfect match to that of the Denisova fingerbone.
That match offers some hope that if researchers can find the same kindof tooth on a fossil skull, or perhaps even a complete skeleton,they’ll be able to see what these ghostly cousins and ancestors lookedlike in real life.
Dr. Bustamante also thinks that other cases of interbreeding are yet tobe discovered. “There’s a lot of possibility out there,” he said. “Butthe only way to get at them is to sequence more of these ancientgenomes.” http://www.nytimes.com/2010/12/23/science/23ancestor.html 
22 December 2010Last updated at 18:03 GMT Scientistssay an entirely separate type of human identified from bones in Siberiaco-existed and interbred with our own species.
The ancient humans have been dubbed Denisovans after the caves in Siberia where their remains were found.
There is also evidence that this group was widespread in Eurasia.
Astudy in Nature journal shows that Denisovans co-existed withNeanderthals and interbred with our species - perhaps around 50,000years ago.
An international group of researcherssequenced a complete genome from one of the ancient hominins(human-like creatures), based on nuclear DNA extracted from a fingerbone.
'Sensational' find Accordingto the researchers, this provides confirmation there were at least fourdistinct types of human in existence when anatomically modern humans (Homo sapiens sapiens) first left their African homeland.
DNA from a tooth (pictured) and a finger bone show the Denisovans were a distinct group Along with modern humans, scientists knew about the Neanderthals and a dwarf human species found on the Indonesian island of Flores nicknamed The Hobbit. To this list, experts must now add the Denisovans.
The implications of the finding have been described by Professor Chris Stringer of the Natural History Museum in London as "nothing short of sensational".
Scientists were able to analyse DNA froma tooth and from a finger bone excavated in the Denisova cave in southern Siberia. The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but evenmore distantly related to us.
The finding adds weight to the theory that a different kind of human could have existed in Eurasia at the same time as our species.
Researchers have had enigmatic fossil evidence to support this view but now theyhave some firm evidence from the genetic study carried out by Professor Svante Paabo of the Max Planck Institute in Leipzig, Germany.
"A species of early human living in Europe evolved," according to Professor Paabo.
"There was a western form that was the Neanderthal and an eastern form, the Denisovans."
The study shows that Denisovans interbred with the ancestors of the present day people of the Melanesian region north and north-east of Australia.Melanesian DNA comprises between 4% and 6% Denisovan DNA.
DavidReich from the Harvard Medical School, who worked with Svante Paabo on the study, says that the fact that Denisovan genes ended up so far south suggests they were widespread across Eurasia: "These populations must have been spread across thousands and thousands of miles," he told BBC News.
One mystery is why the Denisovan genes are unique in modern Melanesians and are not found in other Eurasian groups that have so far been sampled.
'Fleeting encounter' Professor Stringer believes it is because there may have been only a fleeting encounter as modern humans migrated through South-East Asia and then onto Melanesia.
The remains were excavated at a cave site in southern Siberia "It could be just 50 Denisovans interbreeding with a thousand modern humans. That would be enough to produce this 5% of those archaic genes being transferred," he said.
"So the impact is there but the number of interbreeding events might have been quite small and quite rare."
No one knows when or how these humans disappeared but, according to Professor Paabo, it is very likely something to do with modern people because all the "archaic" humans, like Denisovans and Neanderthals disappeared sometime after Homo sapiens sapiens appeared on the scene.
"Itis fascinating to see direct evidence that these archaic species didexist (alongside us) and it's only for the last few tens of thousands of years that is unique in our history that we are alone on this planet and we have no close relatives with us anymore," he said.
The study follows a paper published earlier this year by Professor Paabo and colleagues that showed there was interbreeding between modern humans and Neanderthals as they emerged from Africa 60,000 years ago.
http://www.bbc.co.uk/news/science-environment-12059564
Neanderthal genes 'survive in us'
By Paul Rincon Science reporter, BBC News
Many people alive today possess some Neanderthal ancestry, according to a landmark scientific study.
The finding has surprised many experts, as previous genetic evidencesuggested the Neanderthals made little or no contribution to ourinheritance.
The result comes from analysis of the Neanderthal genome - the "instruction manual" describing how these ancient humans were put together.
Between 1% and 4% of the Eurasian human genome seems to come from Neanderthals.
Butthe study confirms living humans overwhelmingly trace their ancestry toa small population of Africans who later spread out across the world.
The most widely-accepted theory of modern human origins - known as Out of Africa - holds that the ancestors of living humans (Homo sapiens) originated in Africa some 200,000 years ago.
Arelatively small group of people then left the continent to populatethe rest of the world between 50,000 and 60,000 years ago.
Whilethe Neanderthal genetic contribution - found in people from Europe,Asia and Oceania - appears to be small, this figure is higher thanprevious genetic analyses have suggested.
"They are not totallyextinct. In some of us they live on, a little bit," said ProfessorSvante Paabo, from the Max Planck Institute for EvolutionaryAnthropology in Leipzig, Germany.
Professor Chris Stringer,research leader in human origins at London's Natural History Museum, isone of the architects of the Out of Africa theory. He told BBC News:"In some ways [the study] confirms what we already knew, in that theNeanderthals look like a separate line.
"But, of course, thereally surprising thing for many of us is the implication that therehas been some interbreeding between Neanderthals and modern humans inthe past."
John Hawks, assistant professor of anthropology at the University ofWisconsin-Madison in the US, told BBC News: "They're us. We're them.
"Itseemed like it was likely to be possible, but I am surprised by theamount. I really was not expecting it to be as high as 4%," he said ofthe genetic contribution from Neanderthals.
The sequencing of the Neanderthal genomeis a landmark scientific achievement, the product of a four-year-longeffort led from Germany's Max Planck Institute but involving many otheruniversities around the world.
The project makes use ofefficient "high-throughput" technology which allows many geneticsequences to be processed at the same time.
The draftNeanderthal sequence contains DNA extracted from the bones of threedifferent Neanderthals found at Vindija Cave in Croatia.
Retrievinggood quality genetic material from remains tens of thousands of yearsold presented many hurdles which had to be overcome.
Thesamples almost always contained only a small amount of Neanderthal DNAamid vast quantities of DNA from bacteria and fungi that colonised theremains after death.
Svante Paabo (pictured here with a Neanderthal skull) led the research effort
The Neanderthal DNA itself had broken down into very short segmentsand had changed chemically. Luckily, the chemical changes were of apredictable nature, allowing the researchers to write software thatcorrected for them.
Writing in Science journal, the researchersdescribe how they compared this draft sequence with the genomes ofmodern people from around the globe.
"The comparison of these two genetic sequences enables us to find out where our genome differs from that of our closest relative," said Professor Paabo.
The results show that the genomes of non-Africans (from Europe,China and New Guinea) are closer to the Neanderthal sequence than arethose from Africa.
The most likely explanation, say theresearchers, is that there was limited mating, or "gene flow", betweenNeanderthals and the ancestors of present-day Eurasians.
Thismust have taken place just as people were leaving Africa, while theywere still part of one pioneering population. This mixing could havetaken place either in North Africa, the Levant or the ArabianPeninsula, say the researchers.
Professor Stringer added: "Anyfunctional significance of these shared genes remains to be determined,but that will certainly be a focus for the next stages of thisfascinating research."
The Out of Africa theory contends that modern humans replaced local "archaic" populations like the Neanderthals.
Butthere are several variations on this idea. The most conservative modelproposes that this replacement took place with no interbreeding betweenmodern humans and Neanderthals.
Unique features
Another version allows for a degree of assimilation, or absorption, of other human types into the Homo sapiens gene pool.
The latest research strongly supports the Out of Africa theory, but it falsifies the most conservative version of events.
Theteam identified more than 70 gene changes that were unique to modernhumans. These genes are implicated in physiology, the development ofthe brain, skin and bone.
The researchers also looked for signsof "selective sweeps" - strong natural selection acting to boost traitsin modern humans. They found 212 regions where positive selection mayhave been taking place.
The scientists are interested indiscovering genes that distinguish modern humans from Neanderthalsbecause they may have given our evolutionary line certain advantagesover the course of evolution.
The most obvious differences werein physique: the muscular, stocky frames of Neanderthals contrastsharply with those of our ancestors. But it is likely there were alsomore subtle differences, in behaviour, for example.
Dr Hawkscommented that the amount of Neanderthal DNA in our genomes seemedhigh: "What it means is that any traits [Neanderthals] had that mighthave been useful in later populations should still be here.
"Sowhen we see that their anatomies are gone, this isn't just chance.Those things that made the Neanderthals apparent to us as a population- those things didn't work. They're gone because they didn't work inthe context of our population."
Researchers hadpreviously thought Europe was the region where Neanderthals and modernhumans were most likely to have exchanged genes. The two human typesoverlapped here for some 10,000 years.
The authors of the paperin Science do not rule out some interbreeding in Europe, but say it wasnot possible to detect this with present scientific methods.
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