Athena Review  Vol.2, no.3:   Recent Finds

DNA distances Neanderthals from modern humans

In spite of growing skeletal and radiocarbon evidence for contemporeignity of late Neanderthals and Early Modern Humans in Europe, new genetic findings from the northern Caucasus argue strongly against any significant interbreeding between them. This is reported in the March 30, 2000 issue of the journal Nature by a team of Russian, Swedish, and Scottish researchers led by Igor Ovchinnikov, Kerstin Lidén, and William Goodwin, who successfully tested mitochondrial DNA (mtDNA) from the rib of a Neanderthal infant from Mezmaiskaya Cave in Russia, near Black Sea.

The infant's rib was radiocarbon dated at 29,195 BP, significantly later than previously published dates for the site of 45-40,000 BP, which were derived from organic material in the layers. The same bone from the well-preserved infant skeleton allowed the determination of 345 base pairs (the nitrogenous bases in DNA of adenine, thymine, guanine, and cytosine). From this data an mtDNA sequence was established allowing the scientists to compare genetics of the skeleton from Mezmaiskaya to that recently tested by Krings et al (1999) from the original type specimen of Neanderthal, found in 1856 at Feldhofer cave in the Neander Valley.

In the first successful extraction of mtDNA from a Neanderthal specimen, Krings et al. (1999) had reported the Neanderthal genome to be outside the range of modern humans. Evidence that Neanderthals did not contribute mtDNA to modern humans was based on their findings of a statistical probability that the two species diverged between 741,000-317,000 years ago.

Now, in the second successful analysis of Neanderthal mtDNA, Ovchinnikov et al. tested for the closeness of Neanderthals and modern European or Caucasoid populations, using well-preserved skeletal samples from the infant found at Mezmaiskaya, and a comparison tree of 1,897 haplotypes derived from 5,846 modern humans.

Two separate laboratories each isolated the same segment of mtDNA from the Mezmaiskaya infant’s rib. Based on computer tree diagram methods of neighbor-joining and parsimony analyses, the researchers found only a 3.48% divergence between Mezmaiskaya and Feldhofer Neanderthals, similar to differences in the three main groups of modern human populations (Negroid, Caucasoid, and Mongoloid). Neither Neanderthal sequence, meanwhile, was closer to European/Caucasoid samples than to samples from other parts of the world, thus not supporting this hypothesis.

Ovchinnikov et al. estimate eastern and western Neanderthals split between 350,000 and 150,000 years ago, and (in accordance with Krings et al.) that modern human and Neanderthal mtDNA diverged between 853,000-365,000 years ago. This supports the “out of Africa” model for the peopling of Europe by anatomically modern humans in the past 50,000 years, a theory advocating little or no mixing of Neanderthal and Caucasoid populations (see articles in the upcoming issue of Athena Review, Vol.2, no.4). The excellent preservation of the Neanderthal infant from Mesmaiskaya makes it probable that further genetic testing can be done.

[Krings et al. Proc. Natl. Acad. Sci. 96, 1999; Ovchinnikov et al., Nature, 404, 30 Mar. 2000]

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