Sometimes what we think we know about the past obscures what the true past is because the elements that we use to construct the past are so contingent upon recent historical furniture.
As an example, it is often stated that the Bushmen of Southern Africa are the most ancient of human populations. By this, one means that they diverged first of all humans from the rest in the great diversified tree of life. But surprisingly, recent work suggests these people may have Middle Eastern ancestry, mediated by East African pastoralists. In other words, these most ancient of ancient humans have also been touched by the great migrations that issued out of the Neolithic hearths. What we thought we knew about the past turns out to be far less interesting than the truth of the matter.
The same general insight applies in many specific circumstances about peoples and individuals. For example, when customers receive myOrigins results, they may be confused as to the dispersed geographic distribution of their ancestry when they believe that they know the provenance of their lineage.
Consider the “Celtic” peoples and their long history. United by a common language, the migrations of these people took them as far afield as Ireland and Turkey. Down to classical times, they were numerous in places as diverse as Spain, France, and Hungary. Do we imagine that the Celts emerged as a homogeneous horde, pulsing out of an urheimat, sweeping away all that came before? Though such a vision might be fitting for a Conan film, it seems unlikely. Rather, almost certainly, they co-opted local elites and peoples as they themselves co-opted in other regions. On the broad plains of the Po, Cisalpine Gaul, the Celtic become the Roman. And probably many of the Celts were themselves descended from the older indigenes of the regione. A similar process of mixing, assembling, and rearranging may have occurred in Spain. Going further back, there has been a suggestion that the Celtic peoples may in fact derive from a migration out of Iberia in deep antiquity, that of the Bell-Beaker culture.
Today, the Celtic languages and explicit Celtic identity persists on Western Europe’s maritime fringe. But this is a shade of the former expanse of these people. What unites these people, past and present, is a cultural-linguistic framework. True, there are almost certainly genetic threads that bind them, but it seems entirely likely that the “Celts” were in fact a biological synthesis in many different locales of indigenous and immigrant populations. What is typical of Celts today may not have been typical of Celts in the past. Therefore, it is likely that there is no distinctive Celtic genetic signature, as opposed to a particular cultural history. And this truth is not just applicable to Celts but to many cultural groups whose existence and self-identity are concrete and real but whose biological constituents are an ad hoc melange, deeply contingent on particular times and places.