An earlier Neanderthal DNA sequence was determined from bones found in Feldhofer Cave in Germany. 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. 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.
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. 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. Different patterns of movement may have caused mitochrondial DNA to diverge more quickly in the past, he says. The new research, he says, just shows interbreeding was not common.