Fossil DNA tells tales of red-haired Neanderthals

Paleontologists are surprised to find such diversity; clues also suggest wider migration.

Scientists probing Neanderthal remains find important clues in DNA. One recent study suggests some of our extinct cousins had pale skin and red hair. Another investigation finds Neanderthals ranged much farther from Europe into Asia than paleontologists have thought.

The key fact is that at least some Neanderthal fossils yield DNA of high enough quality to tell such tales. Last month, members of an international research team led by Carles Lalueza-Fox at the University of Barcelona in Spain explained in the journal Nature why they think recovering specific DNA sequences from extinct species "can potentially provide information" as to what the species looked like. They backed up this hypothesis with analysis of DNA from two Neanderthal fossils.

They found genetic information similar to, but distinct from, the genes governing skin and hair color in modern humans. They say this "suggests that Neanderthals varied in pigmentation levels" just as we do. That includes the pale skin and red hair that evolved largely in Europe. The team adds that the data suggest this potential "evolved independently in both modern humans and Neanderthals."

Meanwhile, Svante Pääbo at Germany's Max Planck Institute for Evolutionary Anthropology in Leipzig and colleagues have traced Neanderthals far into Asia.

Professor Pääbo's team hit pay dirt as far east as Uzbekistan and the Altai region of southern Siberia. They reported last month in Nature that DNA sequences from hominid fossils found there "fall within European Neanderthal [DNA] variation." They note that this shows "the geographic range of Neanderthals is likely to have extended at least 2,000 km [1,200 miles] farther to the east than commonly assumed."

All Neanderthal DNA sleuths are challenged to distinguish Neanderthal DNA from our own. They have to guard against contamination with modern human DNA. It creeps in from the environment or from mishandling the evidence. It's all too easy to mistake "us" for "them."

That ever-present hazard has dulled the luster of a Pääbo-led study reported in Nature last year claiming that Neanderthal DNA reflects interbreeding with humans. Comparable research reported simultaneously in the journal Science by Edward Rubin of the Joint Genome Institute in Walnut Creek, Calif., and colleagues found no such indication. Then Jeffrey Wall at the University of California in San Francisco took another look at the Pääbo study's data. His reanalysis, published last August in PloS Genetics, indicated that about 80 percent of that supposed "Neanderthal" DNA probably is modern human.

The Pääbo team has acknowledged at least some contamination. It is reanalyzing the data to see to what extent this undermines the suggestion of interbreeding between Neanderthals and modern humans.

Contamination with foreign DNA may also explain why the Pääbo and Rubin teams got different dates for the split between Neanderthals and us. The former team estimates we went our separate evolutionary ways 516,000 years ago. The latter puts the split 706,000 years in the past. Wall's analysis agrees with the Rubin team's date of 706,000 years.

It's early days for this kind of research. The reports a year ago were the first published studies of Neanderthal nuclear DNA. Now we have pale skin and red hair. A new chapter in the history of hominid evolution is being written.

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