最新一期英國《自然》雜志刊登研究報告說,，對俄羅斯西伯利亞一個山洞里發(fā)現(xiàn)的古人類化石進行基因檢測顯示，它不同于現(xiàn)代人和任何已知的古人種,，很可能是一種前所未知的古人種。
報告說,，俄羅斯研究人員早在2008年就在該山洞中發(fā)掘出這塊指骨化石,，但起初認為它是已研究較多的古人種尼安德特人留下的。后來,，這塊化石被送到德國進行基因檢測,，對其線粒體DNA的分析結果顯示，它不屬于現(xiàn)代人和任何已知的古人種,。
尼安德特人生活在大約12萬年到3萬年前,。據(jù)介紹，在線粒體DNA對比上,，尼安德特人與現(xiàn)代人有202處差異,，而這塊化石與現(xiàn)代人有385處差異,，研究人員因此推斷它所屬人種的生存年代比尼安德特人更早，應該大約在100萬年前,。
有專家認為,，單憑線粒體DNA還不能確認這就是一種未知的古人種。為此,，研究人員尚未為其命名,，且計劃對這塊化石進行基因組測序。如果完整基因組測序顯示它真屬于一個未知的古人種,，這將是首次通過基因手段確認人種,，也將是迄今完成的對最古老人類的基因組測序。（生物谷Bioon.com）
生物谷推薦原文：
Nature doi:10.1038/464472a
Fossil finger points to new human species
Rex Dalton
In the summer of 2008, Russian researchers dug up a sliver of human finger bone from an isolated Siberian cave. The team stored it away for later testing, assuming that the nondescript fragment came from one of the Neanderthals who left a welter of tools in the cave between 30,000 and 48,000 years ago. Nothing about the bone shard seemed extraordinary.
A finger bone found in Denisova Cave in Siberia could add a branch to the human family tree.B. VIOLAIts genetic material told another story. When German researchers extracted and sequenced DNA from the fossil, they found that it did not match that of Neanderthals — or of modern humans, which were also living nearby at the time. The genetic data, published online in Nature1, reveal that the bone may belong to a previously unrecognized, extinct human species that migrated out of Africa long before our known relatives.
"This really surpassed our hopes," says Svante P??bo, senior author on the international study and director of evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "I almost could not believe it. It sounded too fantastic to be true."
Researchers not involved in the work applauded the findings but cautioned against drawing too many conclusions from a single study. "With the data in hand, you cannot claim the discovery of a new species," says Eske Willerslev, an evolutionary biologist and director of the Centre for GeoGenetics at the University of Copenhagen.
“I almost could not believe it. It sounded too fantastic to be true.”
If further work does support the initial conclusions, the discovery would mark the first time that an extinct human relative had been identified by DNA analysis. It would also suggest that ice-age humans were more diverse than had been thought. Since the late nineteenth century, researchers have known that two species of Homo — Neanderthals and modern humans — coexisted during the later part of the last ice age. In 2003, a third species, Homo floresiensis, was discovered on the island of Flores in Indonesia, but there has been no sign of this tiny 'hobbit' elsewhere. The relative identified in Siberia, however, raises the possibility that several Homo species ranged across Europe and Asia, overlapping with the direct ancestors of modern people.
The Siberian site in the Altai Mountains, called Denisova Cave, was already known as a rich source of Mousterian and Levallois artefacts, two styles of tool attributed to Neanderthals. For more than a decade, Russian scientists from the Institute of Archaeology and Ethnology in Novosibirsk have been searching for the toolmakers' bones. They discovered several bone specimens, handling each potentially important new find with gloves to prevent contamination with modern human DNA. The bones' own DNA could then be extracted and analysed.
When the finger bone was discovered, "we didn't pay special attention to it", says archaeologist Michael Shunkov of the Novosibirsk institute. But P??bo had established a relationship with the Russian team years before to gather material for genetic testing from ice-age humans. After obtaining the bone, the German team extracted the bone's genetic material and sequenced its mitochondrial DNA (mtDNA) — the most abundant kind of DNA and the best bet for getting an undegraded sequence from ancient tissue.
