of passing interest regarding -perhaps, our 'specialness'? -but we are a single life-form.
Science 26 October 2007 Science Magazine
News of the Week
Ancient DNA Reveals Neandertals With Red Hair, Fair Complexions
What would it have been like to meet a Neandertal? Researchers have hypothesized answers for decades, seeking to put flesh on ancient bones. But fossils are silent on many traits, from hair and skin color to speech and personality.
Personality will have to wait, but in a paper published online in Science this week (www.sciencemag.org/cgi/content/abstract/1147417), an international team announces that it has extracted a pigmentation gene, mc1r, from the bones of
two Neandertals. The researchers conclude that at least some Neandertals had pale skin and red hair, similar to some of the Homo sapiens who today inhabit their European homeland. The paper comes on the heels of one that used similar techniques to show
that Neandertals shared the modern human form of the only gene so far known to influence human speech, FOXP2. Although researchers are working to sequence the entire Neandertal genome (Science, 17 November 2006, p. 1068), these are the first specific
nuclear genes to be retrieved. "These are the two genes you'd most like to see from a Neandertal," explains Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the FOXP2 study.
Figure 1 Ginger man. Some Neandertals had red hair and pale skin, as seen in this reconstruction of a French fossil.
CREDIT: RECONSTRUCTIONS AND PHOTOGRAPHY BY JOHN GURCHE
The mc1r paper is "logical, elegant, and convincing," says anthropologist Nina Jablonski of Pennsylvania State University in University Park. "It's a great paper," agrees molecular geneticist and pigmentation expert Rick Sturm of the
University of Queensland in St. Lucia, Australia.
Many of the Neandertals cavorting in museum dioramas around the world already have pale skin or red hair, because anthropologists have long predicted this coloration on the basis of evolutionary theory. The dark skin beneficial in
Africa offers no advantage at high latitudes, and in cloudy Europe, pale skin facilitates vitamin D production, Jablonski says. But there was no proof of Neandertals' looks until a team led by Carles Lalueza-Fox of the University of Barcelona in Spain
and Holger Rämpler of the University of Leipzig in Germany set out to retrieve the mc1r gene from a 43,000-year-old Neandertal from El Sidrón, Spain, and a 50,000-year-old specimen from Monti Lessini, Italy.
MC1R is a cell membrane receptor that helps regulate the balance between red-and-yellow-colored pheomelanin and black-and-brown-colored eumelanin. Living people with variations that make the receptor work poorly tend to have red hair
and pale skin, although other pigmentation genes also have strong effects (Science, 2 March, p. 1215).
Using the polymerase chain reaction (PCR) to target and amplify the gene, the researchers found a point mutation not seen in living humans. They checked about 3700 people, including everyone involved in the project, to be sure that the variant was unique
to Neandertals. Next, they explored the variant's function by expressing it in human cells and found that it impaired the receptor's activity. "If you have a variant with this low action in modern humans, you get classically Irish-looking red hair and
pale skin" in homozygotes, people with two copies of the variant, says team member Michael Hofreiter of the Max Planck Institute in Leipzig. The researchers calculate that at least 1 in 100 Neandertals would have been homozygotes. Thus Neandertals and
Homo sapiens in Europe followed independent evolutionary paths to a similar phenotype, Lalueza-Fox says.
"I'm convinced that what they're saying is real," says Sturm, who has used similar functional assays to check mc1r variants in living people. Lalueza-Fox adds that Neandertals may have carried a variety of changes in mc1r, as we do, and
so may have had a spectrum of skin and hair colors.
Pääbo and colleagues also used targeted PCR to isolate the FOXP2 gene. They chose FOXP2 because people with mutations in the gene have impaired speech. Pääbo's team had previously traced the gene in living people and suggested that the
unique human variant was selected relatively recently, less than 200,000 years ago--long after Neandertals and modern humans had diverged (Science, 16 August 2002, p. 1105). The implication was that Neandertals lacked the modern human form, Pääbo
But to their surprise, that's not what they found when they sequenced the gene from two bones from El Sidrón, where Lalueza-Fox runs a "clean" excavation for DNA analysis. Both bones carried the modern human version of FOXP2. That
doesn't necessarily mean Neandertals spoke as we do, because many genes presumably influence speech. But "from the point of view of the one gene we know, there's nothing to say that Neandertals were different from us" in their language abilities, Pääbo
Because the Neandertal FOXP2 gene matched that found in living people, Pääbo's team used extra controls to try to rule out contamination with modern human DNA. For example, they sequenced the Neandertal Y chromosome and found that it
differed from that of living men at five key sites. No contamination of the Y chromosome strengthens the case that the FOXP2 result is real, Pääbo says.
The Y chromosome finding also argues against interbreeding between Neandertals and the modern humans then entering Europe. "I find it paradoxical in some ways," says Lalueza-Fox, who is an author of both studies. "The papers make
Neandertals more like modern Europeans, with light skin and hair color and language abilities, and yet there are no signs of interbreeding with modern humans."
But others aren't yet ready to concede that either contamination or mixing has been completely ruled out. "The additional controls give one more confidence that contamination is not a problem, but we can't be 100% sure," says
evolutionary geneticist Jeff Wall of the University of California, San Francisco, who in August reported what he saw as contamination in Pääbo's group's bulk Neandertal sequencing (ScienceNOW, 29 August,
Wall adds that if the FOXP2result is real, it's possible that Neandertals acquired the human FOXP2variant by mixing. "If there was admixture, it wasn't very much. But we can't tell if there was a small amount." Pääbo says he can't rule
out that scenario but considers it "unlikely," given the genetic data so far.