Spit in a tube, stick it in the mail, and several weeks and $99 later, 23andme can tell you just how Neandertal you are. For the average client of European ancestry, an estimated 2.6% of the genome can be traced back to Neandertal ancestors. If you are one of the people carrying around this vague signature of a Neandertal past, you may wonder what it all means. Does a Neandertal ancestor account for your pronounced brow? Or your red hair? Until recently, nobody really had any answers. Things are starting to change, however. In a recent article in Molecular Biology and Evolution, scientist Fernando Mendez and colleagues revealed a specific gene that has been influenced by Neandertal forbears.
The variants are present in a gene cluster called OAS which plays a role in immunity. Mendez noticed that a variant found in modern humans closely resembled that present in the Neandertal genome, which has been published. And while Neandertals and humans parted evolutionary ways around 300,000 YBP, this genetic variant in the OAS cluster was found to have diverged from Neandertal sequences only 125,000 YBP. Finally, this variant is found in people from Eurasia and North Africa, but not SubSaharan Africa, consistent with the area where Neandertals were once found. Pretty neat, huh?
And this is not the first gene that appears to have come from Neandertals! Last year, Mendez and colleagues identified Neandertal variants in another gene called STAT2. This gene, too, is involved in immunity. Although no one is sure what the functional importance of the Neandertal version of the OAS and STAT2 genes are, one interesting finding is that alternate versions of both of these genes also appear to have entered our genomes from interbreeding with Denisovans, another type of archaic human that is known only from a single bone recovered from a cave in Siberia. This has led researchers to question whether some alleles, like those involved in immunity, may be especially likely to get passed along after a romantic episode with a mysterious stranger belonging to another species. It seems likely that in the future, additional genes that have been passed down from Neandertal ancestors will be identified.
There have been some fantastic articles about the research supporting human-Neandertal interbreeding recently. One was Sleeping With the Enemy, an article by Elizabeth Kolbert that appeared in the New Yorker in 2011–it focuses on Svante Paabo’s work. Another article appeared in Scientific American last month. It was by Michael Hammer, one of the scientists involved in the work I discussed here. It’s called Sex with Other Human Species Might Have Been Secret of Homo Sapiens’s Success, and it’s definitely worth a read.