The most famous reconstruction of Kennewick Man is strange because it resembles British actor Patrick Stewart. Humans use phenotypes, morphology, to ascertain genetic relatedness when DNA is not available. In the 1990s DNA was not available. The inference by many researchers who had access to the remains was that Kennewick Man was different because his morphology may have resembled a person of European heritage. The controversy turned into such a circus that somehow Steve McNallen, arguably America’s foremost Northern European neo-pagan expositor, made claims on the remains on the same grounds as Native American people! Later scholars suggest that perhaps Kennewick Man was not so much European, as not typical of contemporary Native Americans (e.g., perhaps he was part of an early migration of basal East Eurasians related to the Jomon of Japan).
If the Seattle Times report is correct, and I believe it is, Kennewick Man is part of the ancestral population to modern Native Americans. This should put to bed most of the political debate, since the results are likely to mollify many Native activists. But, there are still details to be fleshed out. A 2012 publication suggests that there was a secondary migration out of Eurasia, which resulted in the Na-Dene group which is common in the northern and western portions of North America. In contrast, Kennewick Man is likely to belong to the first ur-North Americans, who arrived as a relatively small population from Berengia ~15,000 years ago. This is the overwhelming majority of indigenous ancestry, and south of the Rio Grande basically the totality.*
The context here is important. One insight of modern ancient DNA is that there has been a great deal of population turnover over the past ~10,000 years, as well as admixture between disparate lineages. When Kennewick Man died ~9,000 years ago Europeans as we understand them did not exist genetically. All across Eurasia, Africa, and Oceania, the Holocene brought radical demographic turnover (with some exceptions such as the Andaman Islands and the deserts of southwest Africa). The New World was somewhat different, as I implied above. There were some demographic disruptions, but south of the Rio Grande, and across the eastern half of North America, the populations descend from a relatively homogeneous founder stock which arrived at the end of the Pleistocene. The fact that many remains seem “atypical” for the morphology of Native Americans is strong evidence of in situ evolution.**
Years ago a physical anthropologist told me that when you look at Amazonian natives they “looked” like Siberians. Yes, they had changed and adapted, but only somewhat. It illustrated to me the powerful constraint of limited genetic variation upon populations. Similarly, though there is variation in pigmentation among native populations in the New World, it is far less than you see in the Old World. Why? Perhaps it is a function of different (or lack thereof) of selective pressures. Or, perhaps the variation wasn’t there for selection in the first place? The history of the Old World has jumbled all our easy narratives. The New World may actually be a godsend because of the simple elegance of its demographic history.
* From my Twitter exchanges with Pontus Skoglund I believe there is some population structure in the founding “First American” group, though not a great deal.
** Admixture is an issue, but that can be obviated by genetic testing, as well as looking at early modern remains.