Gene Expression

Since I will be writing a great deal about Neandertals, please keep this image in your mind. I know that most readers of this blog don't view Neandertals as chimps, but I check google news for evolution and genetics related topics and the recent spate of articles on archaic genomics did spawn a few "Neandertals closer to chimpanzees" pieces. Those of you versed in cladistics, or any sort of taxonomy, are likely outraged, but that's just how it is. The photo to the left is of a child, and perhaps "humanized" a bit too much, but Neandertals were clearly humans. The child has light skin, hair and eyes, something one might expect from a lineage which was resident in Europe for nearly 1 million years. The MC1R locus which controls aspects of pigment production is extremely polymorphic in Europeans. If you run a coalscent simulation it seems that this gene would have needed nearly 1 million years to build up as much diversity as you see in Europe if one assumes selective neutrality (if you model it as a loss of function, so a relaxed selective regime, then it is an acceptable hypothesis). The alternative hypothesis is a form of negative frequency dependent selection for novelty which would result in phenotypic and genetic diversification. The former option clearly points to the possibility that the diversity in MC1R might be due to the absorption of a Neandertal element into the early H. sapiens sapiens population of Europe. The only caution I would add is that some of the alleles for light skin and eye color might be under only recent selection within the last 10,000 years in Europe. So Neandertals might have been as swarthy as the typical Inuit, who knows? I would be willing to bet that Neandertals had light skin and hair though, the two are somewhat related, and MC1R does have a strong relationship to red hair. Eye color is sketchier, and unlike light hair it seems to be evident only in European or near-European populations. Interesting times....