The concept of continuity/discontinuity is essential in any science attempting to study human past. Archaeologists, for example, try to determine whether a given material culture had a local origin or was brought from somewhere else, producing a break in the the continuum of cultural elements. For historical linguists it is essential to establish the length of time that a given language or group of languages was or has been spoken in a given territory, and whether they're the result of continuity or 'substitution'. On the other hand, population geneticists try to produce maps where genes and human populations are distributed along a timeline of thousands of years, trying to reveal the actual story of human origins and migration. In principle, the results obtained in these scientific disciplines are independent of each other; establishing the continuity of a prehistorical material culture does not necessarily imply the continuity of a language; population discontinuity caused by migration does not necessarily involve language discontinuity, and so on. However, it is sometimes possible to put the various types of data together in search of common patterns. This, in fact, is possibly one of the main challenges for the human sciences at present and in the future.
In this blog I have often written about continuity/discontinuity in language, and have also drawn some paralellisms with population studies and archaeology. Today I want to focus on population genetics in particular. Or more exactly, on the patterns of genetic continuity/discontinuity in Europe.
Are modern Europeans the descendants of the people who lived in their area in the Paleolithic, or is their genetic heritage the result of later migrations? This basic question has kept a couple of generations of population geneticists quite busy, and it seems that a general agreement is far from being reached. Some authors, e.g. Bryan Sykes and Steven Oppenheimer, have proposed that most of the genetic material of modern Europeans can be traced back to local Paleolithic populations. Others think that the percentage of genetic input from later migration is higher. One of the most important factors affecting this issue is the type of technology or methodology used in the analysis. The pioneering studies of Cavalli-Sforza in the 1960s, which seemed to support the Neolithic demic diffusion model, may now be considered obsolete, especially because of the dated technology used then. These technologies are improved and multiplied constantly, including for example the possibility of analysing 'old bones', i.e. the genetic material found in ancient human remains; as a consequence, the debate on the origins of European populations has become more complex, and indeed quite interesting. A new theory is proposed one day and the next there is new contradictory evidence found by means of a more accurate technique. Needless to say, it is difficult for a non-geneticist to follow these developments, but ayone studying language prehistory must be aware of this debate.
As I said earlier, Steven Oppenheimer can be seen as one of the proponents of the indigenist theory of European populations. I have recently read a couple of blog posts (this one and this one) whose auhtor, Dienekes Pontikos, provides evidence against the indigenous theory and the validity of Oppenheimer's methodology. He goes as far as to say that the indigenous theory has definitely been 'demolished', and that the genetic components of modern European populations derive mostly from post-Paleolithic migratory events. He offers links to some recent articles written by geneticists who would support this migrationist view. What do I make of all this? I am sure that there must be some faults in Oppenheimer's methodology, and that some of his conclusions can be revised or even refuted, as usually happens in the scientific domain, but I am not so sure that the counter-arguments used by Dienekes are as conclusive as he claims them to be. These two posts have generated a massive amount of comments (222 in one case), sometimes from people who are currently researching on population genetics, and it seems that the indigenous/migrationist debate is still open. And it will be so in the future, with the development of newer techniques. Now we are in November 2009. What can we say about European population genetics? Can we give numbers, percentages of 'indigenous genes' versus 'migration genes'? Let's take the Basque Country, Switzerland, Lazio, Greece or any other European area. Is it possible to determine whether the current populations of these areas are to a greater or lesser extent the descendants of the people who lived there in the Paleolithic? Or is the role of migration greater than some cholars thought a few years ago? I think the answer to these questions is not clear yet.