A Free Man

Neanderthals are our hominid relatives with whom we shared the Mediterranean region for several thousand years before began to be supplanted by modern man around 45,000 years ago and became extinct shortly thereafter. There are a number of questions regarding their fate, the biggest being why modern humans were ultimately more successful than neanderthals. Some scientist believe that it was modern man’s ability to use spoken communication that allowed us to outcompete (or kill off) the Neanderthals. Another interesting hypothesis, that makes research into the genetic nature of Neanderthals quite current, is that climate change was a major factor in their extinction. But beyond this topical coincidence, any evolutionary comparison that we can make between modern humans and another member of genus Homo is in itself interesting. Most of the comparisons that we use today are between humans and the apes, a more closely related hominid is a valuable tool in answering questions about our origins.Two recent papers describe research that attempt to make some such comparisons. Earlier this month in Current Biology a multi-national group led by Johannes Krause from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany describes genetic evidence that suggests that Neanderthals may have been capable of more advanced communication than previously thought. A second study led by Carles Lalueza-Fox of the University of Barcelona and Holger Rompler of the University of Leipzig, coming out later this week in Science, postulates about variations in the complexion of Neanderthal man.Both of these studies employ a technique known as the polymerase chain reaction (PCR). In short, this is an extremely sensitive method of copying and amplifying short sequences of DNA. Once a PCR product is generated it can be sequenced using a related technique allowing a researcher to read the letters of DNA in which he is interested. PCR is used for all sorts of molecular biology, but it has proved very valuable in gaining information about extinct species. This is because DNA is a fairly stable molecule and may be well preserved in tissue (even bone) that has been in a cool dry environment. Because PCR is a sensitive technique, even a minute amount of DNA can be used as a template for amplification in sequencing. Researchers have been able to use PCR to glean sequence information about extinct species such as the woolly mammoth which allows them to compare the extinct mammoth with extant relatives like the elephant.Using PCR, the researcher that did this recent work were able to look at two Neanderthal genes and compare them with the human The conclusions in these two papers are straightforward. In the upcoming Science paper, the researchers amplify and sequence a fragment of the melanocortin 1 receptor (MC1R) from two samples of Neanderthal remains. This gene is involved in regulation skin and hair pigmentation. The variant of this gene that was found in the Neanderthal samples would result in reduced MC1R activity and has not been found in human samples. This suggests that some Neanderthals had fair skin and maybe red hair, suggesting that some Neanderthals looked like the second picture in this post running contrary to the established picture that we have of Neanderthal man represented in the first image. The second study, from Current Biology, focuses on a gene that has been implicated in development of speech and language. FOXP2 is the only gene that is known to have a specific role in human speech and there are two mutations in the human version of the gene that make it different from the chimpanzee version. Inactivation of FOXP2 results in severe problems in facial movement and language processing. Most researchers, based on anatomical studies, have hypothesized that Neanderthals did not have an advanced spoken language. Under that hypothesis, the FOXP2 gene in Neanderthals should be more similar to other primates like chimpanzees than to humans. Surprisingly, this is not the case, in fact the Neanderthal gene carries two features that are thought to characterize the human version of this gene. This does not necessarily mean that Neanderthals used a spoken language, but it does suggest that these changes occurred much earlier and that we may have more in common with Neanderthal man than previously hypothesized.However, this type of analysis is fraught with problems. It is difficult to extract DNA from ancient samples as the tissue and the DNA is prone to degradation. The use of PCR is essential for these types of analyses, but the sensitivity that makes it so useful also renders it dangerously error prone. It just takes one molecule of contaminating DNA to yield false data that can ruin a study. Particularly in this case because Neanderthals and modern humans belong to the same genus, their DNA is nearly identical. It is extremely difficult to tell the difference between genuine data from Neanderthals and contamination from researchers. Both of these studies employ controls in an attempt to insure that the sequences that they focus on are not contaminants. However, a recent paper by Wall & Kim in PLoS Genetics claims that previous work from the same group that published the Current Biology paper was fraught with error. To be quite honest, many of the problems that Wall & Kim point out have not been resolved in either of these papers and I am not convinced that their conclusions are completely reliable. What’s even more surprising is that one of them made Science even though this type of study has been previously published in that journal and the integrity of the experiments called into question.The real take home message from these studies may be that we’re not quite at the point that we can undertake these type of analyses with the existing technology. It is certainly a valid line of research and could be extremely informative about human evolution, specifically what advantage Homo sapiens had that allowed us to flourish while the Neanderthals died out. To get any real information, however, it is crucial that the data we collect is free of error - we’re not quite at that point yet.Image credits:Neanderthal child Neanderthal with spearNeanderthal mug shot

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