8 November 2009

Migrations in prehistory

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.


Joan-Carles Martí i Casanova said...

Interesting reading. The fact that Latin spread over such a wide area: giving birth to Romance languages; or that French and English are spoken -as native languages- by peoples of different races, colours and continents should be enough evidence. I once smiled on a plane because the man seated next to me told me that Spain was his "madre patria". The man looked outrageously native of the Americas long before Columbus set his foot over there.
And yet -let me start with a "and"-aren't we all pretty much the same and which are the real genetic differences amongst Europeans?

Being no expert it would seem that language and genetics in a huge shared swimming pool -such as been the case in the European continent for several thousands of years- are a difficult set to match.

Yet, you will always find those who defend "pockets" of genetic purity here and there: perhaps the Scandinavians (until the 1960s at least!), surely not the Basque nor other tribes in Northern Hispania: the fact is that, as Valencians, we are four at home and each one of us could be misplaced in a different place according to genetic clichés: my son could pass for a North African Semitic type being dark even for a Spaniard, my wife for an Alpine shepherdess somewhere in Northern Italy, with her broad face, tall and stocky and green eyes; my daughter could have been sung by an Occitan troubadour with her curly blondish hair and her thin almost Germanic frame and I will pass for an Englishman, a Frenchman, an Italian or a Spaniard depending on the hat and shoes I decide to wear that day and just how much sun I've recevied that year since I can go from milky white to a dark tan that doesn't usually last very long. We all, of course, speak the same Romance Elxan traditional Catalan variety at home.
I'm still extremely curious about all these human flows, which mean really little to present day Europeans. The future is of course even more mingled.

Jesús Sanchis said...

Trying to understand the prehistory of humanity is not an easy job, and population genetics is one of the tools that scientists can use to try to understand it. There's always a danger that scientific data might be used by some people as cheap arguments to defend their nationalistic or racist claims, but that is something that should be avoided. Population genetics is a fast-growing science, also a relatively young one, and its results must be taken with a pinch of salt. But it would make no sense to ignore population genetics data if we want to study the languages of prehistory. For some centuries, it has been customary to explain the expansion of language groups, i.e. Indo-European, as the result of massive migration or conquest in prehistory. If we want to test these theories, it is clear that genetic data might be relevant. And also if we want to test a non-migrationist theory.

Joan-Carles Martí i Casanova said...

I agree and there is nothing wrong to all that.
I'm certanly interested and it makes me only more curious.
It's a whole new field for me and I would highly appreciate your guidance as to what has been published on the matter.

Luca Miccolis said...

I appreciate the contents of this blog and, as an amateur, I found very interesting that the Continuity Theory is becoming matter of debate, even if rarely is treated in university classes.

An important contribution about the CT is given by Marcel Otte, a professor of Prehistory at the Université de Liège, who, first in 1994, started to make the hypothesis that the spread of Indo-European languages was to connect with a population wave in the Paleolithic period.
In his paper “Did Indo-European languages spread before farming?” (1999) written together Jonathan Adams he hypothesises that a reduction in population density across
most of the region during the coldest part of the Younger Dryas (around 12,800-11,400 cal.
y.a.) may have been followed by a sudden rebound phase, when climate switched back to
warm, moist Holocene conditions over only a few decades. A 'sparse wave' of hunter-gatherers
migrating rapidly out of a refugial area (located in southern Europe and/or the Near East) would have made a contribution to the genetic and linguistic legacy of the region. This may explain part of the initial prehistoric dispersal pattern of the Indo- European languages.
Moreover Otte says it is also necessary to bear in mind the possibility that the population increase, causing the initial phase of spread the Indo-European languages, occurred at the earlier warming event at the end of the Last Glacial Maximum.

In “Arguments for Population Movement of Anatomically Modern Humans from Central Asia to Europe” (2007) he points the attentions to the Aurignatian culture associated to the first anatomical modern humans that reached Europe (Cro-Magnon): this massive migration of modern humans was the only one during the Palaeolithic to correspond to a demographic movement of external origin, and thus the basis for the future ‘Indo-Europeans’.
As a personal opinion, I think that the Gravettian culture, spread in Europe about 22.000 BP, could have been the ‘responsible’ of Indo-European languages but, as I said, I am an amateur and I have no means to make research about this!
I hope that all these arguments, together to the linguistic theories of Alinei, shall contribute to a wider and clearer scenario to understand the origin of peopling of Europe and its languages.

Jesús Sanchis said...

Hello Luca, and welcome to this blog.

Some years ago, the idea that PIE expansion had started about 4,000 BC, or even later, was basically undisputed. However, scholars like Renfrew and Alinei have proposed other possible scenarios and chronologies, dating PIE expansion in the Neolithic or in the Paleolithic. Their theories must still be tested and refined, and it is early to say if they right or not, but one thing is for sure: they have shown that the traditional approach is based on assumptions that might be quite wrong.

Andrew Oh-Willeke said...

The argument for migration (e.g. one people largely replacing another) in the Neolithic Revolution is most strongly supported by ancient DNA. Genetically, Upper Paleolithic hunter-gatherers were very different from the early Neolithic farmers who had strong genetic ties to the Near East (who, in turn, differ materially from the people who live there today).

The ancient DNA evidence holds not only for ancient human DNA, but also for ancient animal DNA from remains at those locations, and, of course, the farming was taking place with crops domesticated in the Near East.

The physical anthropology (i.e. skeletal shape) evidence likewise supports population replacement.