IGOR V. OVCHINNIKOV, ANDERS GÖTHERSTRÖM, GALINA P. ROMANOVA, VITALIY M. KHARITONOV, KERSTIN LIDÉN & WILLIAM GOODWIN
Molecular analysis of Neanderthal DNA from the northern Caucasus
Nature 404, 490 - 493 (2000)
© Macmillan Publishers Ltd.
The expansion of premodern humans into western and eastern Europe 40,000 years before the present led to the eventual replacement of the Neanderthals by modern humans 28,000 years ago. Here we report the second mitochondrial DNA (mtDNA) analysis of a Neanderthal, and the first such analysis on clearly dated Neanderthal remains. The specimen is from one of the eastern-most Neanderthal populations, recovered from Mezmaiskaya Cave in the northern Caucasus. Radiocarbon dating estimated the specimen to be 29,000 years old and therefore from one of the latest living Neanderthals. The sequence shows 3.48% divergence from the Feldhofer Neanderthal. Phylogenetic analysis places the two Neanderthals from the Caucasus and western Germany together in a clade that is distinct from modern humans, suggesting that their mtDNA types have not contributed to the modern human mtDNA pool. Comparison with modern populations provides no evidence for the multiregional hypothesis of modern human evolution.
DNA Tests: Humans Not Descended from Neanderthals
By Kenneth Chang
DNA from the bones of a Neanderthal baby who died 29,000 years ago offers further
evidence that Neanderthals are cousins rather than ancestors of modern humans.
Writing in Thursday’s issue of the journal Nature, William Goodwin of the University of Glasgow in Scotland, along with collaborators from Russia and Sweden, report that the baby’s DNA is much more similar to another Neanderthal DNA sequence reported in 1997 than to that of modern humans.
Evolution or Replacement?
Some anthropologists have argued that people evolved at least partly from the Neanderthals. The opposing theory is that modern humans evolved in Africa, then spread outward, overwhelming earlier hominids including Neanderthals. The short, squat Neanderthals inhabited much of Europe from about 100,000 years ago until dying out about 28,000 years ago.
"Neanderthal DNA is distinct from modern humans," Goodwin says, "and there are no examples of humans having Neanderthal-type DNA."
The researchers isolated segments of DNA from the baby’s mitochondria — small, energy-producing bodies within a cell that contain their own genetic code separate the main DNA strand in the nucleus of the cell. Mitochondrial DNA is easier to study, because each cell contains about 1,000 mitochondria, meaning there are about 1,000 times more DNA strands to extract. Unlike cell DNA, mitochondrial DNA is inherited only from the mother.
Not Human Enough
The baby’s mitochondrial DNA differed from that of the other Neanderthal in 3.5 percent of the locations tested, while the divergence from humans was 7 percent. Scientists consider that to be a substantial gap. "It all points away from the Neanderthal," Goodwin says.
Based on the number of differences, and the expected rate of change, Neanderthals and humans last shared a common ancestor about 500,000 years ago, the researchers say.
The Neanderthal DNA was also no more similar to the DNA of Europeans than people elsewhere, which might have been expected if Neanderthals had mated in large numbers with their human neighbors in Europe.
The baby, found in Russia’s Caucasus Mountains, has been estimated in age at somewhere between an unborn 7-month-old fetus and a newborn of a couple of months. Molecular biologist Matthias Hoss, an expert in ancient remains now working at the Swiss Institute for Cancer Research, said the research appears to support the theory that Neanderthals were an evolutionary dead end.
"This adds quite a lot of confidence that the Neanderthal didn’t contribute to modern populations," he said.
Loring Brace, an anthropologist at University of Michigan and a proponent of the idea that people descended from Neanderthals — he argues that features of skulls show a steady progression from Neanderthal to human — says the DNA evidence does not sway him. Different patterns of movement may have caused mitochrondial DNA to diverge more quickly in the past, he says. "The whole picture is still very spotty," Brace says.
Erik Trinkaus, an anthropologist at Washington University in St. Louis, says the DNA evidence does not disprove his assertion that the 25,000-year-old skeleton of child unearthed in Portugal is the descendent of a human-Neanderthal hybrid. The new research, he says, just shows interbreeding was not common.
"There is no contradiction," he says.
Goodwin also says his finding isn’t the final word. Perhaps Neanderthals and humans mated and produced sterile offspring, similar to mules, the crossbreed of horses and donkeys. "It’s very hard to prove any negative," Goodwin says. "I wouldn’t claim this to be conclusive."
Maintained by Francis F. Steen, Communication Studies, University of California Los Angeles