The authors are even more circumspect in their abstract: "The C1 lineage was present in the Icelandic mtDNA pool at least 300 years ago. This raised the intriguing possibility that the Icelandic C1 lineage could be traced to Viking voyages to the Americas that commenced in the 10th century. In an attempt to shed further light on the entry date of the C1 lineage into the Icelandic mtDNA pool and its geographical origin, we used the deCODEGenetics genealogical database to identify additional matrilineal ancestors that carry the C1 lineage and then sequenced the complete mtDNA genome of 11 contemporary C1 carriers from four different matrilines. Our results indicate a latest possible arrival date in Iceland of just prior to 1700 and a likely arrival date centuries earlier. Most surprisingly, we demonstrate that the Icelandic C1 lineage does not belong to any of the four known subclades of haplogroup C1. Rather, it is presently the only known member of a new subclade, C1e. While a Native American origin seems most likely for C1e, an Asian or European origin cannot be ruled out."
Why can Asian or European origins not be ruled out? The authors note that the particular C1 lineage found in Iceland is "exceedingly rare" in European populations where mtDNA variation has been the subject of "dense sampling." This therefore "weighs against a hypothesis of antiquity in Europe." However, C1e has not to date been found among Native American populations. (C1a has been found only among East Asians, and C1b, C1c, and C1d only among Native Americans). But that is not a good indication that the Iceland mtDNA C subclade did not originally derive from an individual from the Americas. Native American populations are under-sampled. It could be here. The authors note a second possibility for its lack of presence here: "Given the rather drastic population size reductions that resulted from the actions of Europeans after 1492, it is quite possible that the C1e lineage was once carried by, but has now been lost from, contemporary individuals with Native American matrilineal ancestry." In short, genocide (my word, maybe not theirs) and disease may have killed off all of the C1e carriers here. Okay, so it is more likely that C1e arrived in Iceland via a body that came from what we call "the Americas" rather than via a human body that traveled from "Asia" or "Europe."
Now, I am not sure why Europeans and their descendants consistently rule out the possibility of human beings from other continents being able to travel vast distances pre-Columbus of their own accord and mindfully, i.e. as more than mammals just accidentally wandering far from home as they followed food (e.g. C1e in Iceland MUST be traced to the Viking voyages). We do have evidence to the contrary of non-European peoples' navigational skills. But leaving that bit of cultural myopia aside, the hypothesis of these anthropological geneticists is not unreasonable. But neither does it justify the interpretations in the press. Witness the ridiculous headlines:
Time Magazine (11/26/10): More Proof that Vikings Were First to America
AFP (11/17/10): Vikings Brought Amerindian to Iceland 1,000 Years Ago: Study
RedOrbit.com (11/18/10) DNA Shows Viking, Amerindian Link to Iceland
I like this one a bit more, it leaves the question of agency an open one, which it is, i.e. who decided to travel and why.
Daily Telegraph (11/16/10): First Americans 'Reached Europe Five Centuries Before Columbus Voyages'
The lesson is not to rely too much on the popular press for your understanding of new scientific findings. I hate to bash science reporters--I know a couple of really good ones, and good venues. I especially like the UK-based New Scientist, usually. This time however they rely on the AFP take and write that Vikings Brought First Native American to Europe. Expected more of you New Scientist.