Showing posts with label Population Genetics. Show all posts
Showing posts with label Population Genetics. Show all posts

1 September 2011

More on Paleolithic proto-Indo-European

They don't usually do it, but sometimes they do, especially when they have to face apparently inexplicable phenomena like the emergence of some language groups (Indo-European, Afro-Asian, etc.) and their mysterious, even transcontinental dispersals at prehistoric times. It is then that some archaeologists feel the need to tackle the issue of ancient languages and devise their own theories. In the field of Indo-European studies, for example, the list is already quite long: Gordon Childe, Marjia Gimbutas (Kurgan theory), James Mallory, Colin Renfrew (Anatolian Hypothesis), Marcel Otte (Paleolithic Continuity), David Anthony, and many others. The debate is still alive, and it involves a number of archaeologists. Let's see an interesting example that I recently found:

Gamble et al (2005: 209; the highlighting is mine): "the most fruitful avenue for advocates of the cognitive origins synthesis to pursue might be the arrival of a proto-Indo-European dialect in southwestern Europe with the Badegoulian ATU2, in the refugium phase, and its subsequent codispersal with the Magdalenian ATU2 into western and northern Europe. It seems unlikely, however, that historical linguists who were not prepared to journey with Renfrew back to the early Neolithic would welcome the concept of a Late Glacial dispersal of Indo-European languages in western Europe."

Sounds like the Paleolithic Continuity hypothesis, doesn't it?

As we can see in the abstract, the authors of the article, among them two notorious British archaeologists (Clive Gamble and Paul Pettitt), criticise the role of historical linguistics and genetics in the debate and also the validity of what they call 'agriculturalist thinking', which was born in the work of Gordon Childe and continued by Colin Renfrew and other archaeologists. Let's see an excerpt from the abstract:

"This article presents the initial results from the S2AGES database of calibrated radiocarbon estimates from western Europe in the period 25,000-10,000 years ago. Our aim is to present a population history of this sub-continental region by providing a chronologically-secure framework for the interpretation of data from genetics and archaeology. (...) We conclude that only archaeology can currently provide the framework for population history and the evaluation of genetic data. Finally, if progress is to be made in the new interdisciplinary field of population history then both disciplines need to refrain from inappropriate agricultural thinking that fosters distorting models of European prehistory, and they should also pay less, if any, attention to historical linguistics."

I'm afraid I agree with them.

- Gamble, Clive, W. Davies, P. Pettitt, L. Hazelwood & M. Richards (2005). "The archaeological and genetic foundations of the European population during the Late Glacial: Implications for 'Agricultural Thinking'. Cambridge Archaeological Journal, 15:2, 193-223.

- Magdalenian art. Lascaux (France).

24 May 2011

The Atlantic zone of Western Europe

I won't be there and it's a pity, because I'd love to. From the 9th to the 11th of June the Centre de Recherche Bretonne et Celtique (University of Brest) organizes a conference about the possible connections across the Atlantic fringe of western Europe. There are contributions from a variety of sciences: archaeology, linguistics, population genetics, and some of the participants are scientists that I have already talked about in this blog, in some cases extensively: Mario Alinei, Stephen Oppenheimer, Marcel Otte, Xaverio Ballester, John Koch, Francesco Benozzo, and some others whose research I would be very interested to know about. It is clear that some of the participants share views that are connected with the Continuity paradigm, something that can be seen very clearly just taking a look at the programme of the conference, with titles like Les Indo-Européens sont venus avec Cro-Magnon (Marcel Otte) or The Atlantic Celts: cumulative evidence from Paleolithic (Alinei- Benozzo).

As I said, I'd really would love to be there, but I can't. Unfortunately, there is no post as 'official blogger of the event' that I could apply for! It's not just the conference, it's also the chance of going to Brittany. In any case, however, I'm planning a trip there in August, so I'll get a chance to visit places like Carnac (see picture) or the Armorican coast.

14 March 2011

Out of southern Africa: the ancestral click

In a previous post I talked about the Out of Africa (OOA) theory, which is the most generally accepted explanation about the origin and dispersal of our species. There are also some alternative views, the so called multirregional theories, and in recent times the original OOA proposal has become more complex, with the addition of possible hybridization between H. Sapiens and other hominid groups, e.g. the Neanderthals, and the possibility of various migration routes from Africa, also with varying chronologies. The debate is still open, but the core of the theory remains the same: our species emerged in Africa some time between 100,000 and 200,000 years ago. Now, whereabouts in Africa exactly?

In a very recent article (Henn et al, 2011, available here) it has been suggested that South Africa is the most likely location of the emergence of Homo Sapiens. The authors used a very large sample of genetic material from various sub-Saharan populations, especially hunter-gatherers. They concluded that the highest level of genetic variability in Africa, and therefore in the world, can be found in some areas of southern Africa. The models of geographic dispersal clearly suggest the same conclusion: (p. 3) "A point of origin in southwestern Africa was approximately 300-1,000 times more likely than in eastern Africa". On the right you can see a map, taken from the article, with a representation of geographic distance deduced from genetic material.

The authors also mention the fact that the suggested original area coincides roughly with the aera where the so-called Khoisan languages are spoken. We would have a very deep chronology based on the genetic diversity of those human populations and the presence of a very peculiar group of languages. The authors don't make any further comments or proposals about the population-language correlation, but the idea is tempting, and it has of course been proposed by other researchers, as we will see later. Now, what is it that makes the Khoisan languages so peculiar? No doubt, the presence of click phonemes, which are not found anywhere else in the world, with only some rare isolated cases in eastern Africa. What does a click sound like? Let's take a first lesson:

The correlation between population divergence and linguistic distribution has led some researchers to think that the Khoisan languages may date to a very early period in our history as a species. In their 2003 article (available here), Knight et al studied the genetic divergence between some of the Khoisan-speaking groups, especially between the San and the Hadzabe. This divergence is so deep that it can only be understood as a very old phenomenon, maybe more than 40,000 yeras old. The authors suggest that the linguistic divergence between those populations could correlate with the genetic variation, and be equally old. According to them , the possibility of an independent 'invention' of a click sound repertoire must be ruled out; therefore, these clicks must have been already present in some kind of proto-Khoisan language that was spoken prior to the San-Hadzabe separation. (p. 471): "The deep genetic divergence between the click-speaking groups is consistent with the hypothesis that clicks are an ancient element of human language", an element which only survived in those original areas and disappeared elsewhere. This hypothesis is in fact a radical proposal of language continuity as it suggests a linguistic survival from beyond the Upper Palaeolithic, but it is nearly impossible to test its validity. Trying to compare hunter-gatherer societies through time, including their languages, is no easy task, and there are other ways of explaining the presence of clicks in those languages (vid. Traunmüller 2003, available here). But it must be admitted that the correlation between the various data (archaeological, genetic and linguistic) is firmly established, which is a good basis for further research and developments. 

- Henn et al (2011). "Hunter-gatherer genomic diversity suggests a southern African origin for modern humans". PNAS, 108 (10).
- Knight et al (2003). "African Y chromosome and mtDNA divergence provides insight into the history of click languages". Current Biology, 13, 464-473.
- Traunmüller (2003). "Clicks and the idea of a human protolanguage". PHONUM, 9, 1-4.

8 May 2010

The Franco-Iberian refuge

During the last glaciation, vast areas of northern Europe, including the British Isles, were uninhabited. This glaciation reached its peak at about 20,000 BC (Late Glacial Maximum, LGM), and it wasn't until the beginning of the Holocene (about 12,000 BP) with milder climatic conditions, that these territories started to be repopulated from southern refugia. Population genetics studies show that the Franco-Iberian LGM Refugium played a major role in this repopulation, with a series of relevant gene clusters that can be traced back to that original area. Some authors, e.g. Oppenheimer, have also suggested that this Mesolithic expansion from the various rrfugia is the most important component in today's European populations; other authors suggest that the role of later oppulation movements, e.g. during the Neolithic, has left a more significant mark. This is of course a matter of current debate, and one that has important implications for the study of European prehistoric languages. Now, what was this Franco-Iberian refuge exactly?

Sometimes, it is referred to simply as the Iberian refuge, but I prefer the other name (Franco-Iberian, or Franco-Cantabrian) because I think it's a more accurate term. In his book (Origins of the British), Stephen Oppenheimer defines it as follows: (p. 118): "The refuge for south-west Europe was spread either side of the Pyrenees in southern and eastern France, the Basque Country, and other northern coastal parts of Spain such as Galicia and Catalonia." I'm not so sure of that. If we take a look at a physical map of the Iberian Peninsula, we realize that it is in general composed of high lands and mountainous terrain. In fact, Spain is the second highest country in Europe, after Switzerland, and the area of Castilla-León, sorrounded by mountains, is the highest plateau in Europe (with cities like Burgos, at an altitude of 929 m.). In present-day climatic conditions, these natural features would impose some limitations to population or linguistic exchange. In the hard conditions of the LGM, and also in later cold spells, e.g. the Younger Dryass, they probably meant complete isolation. The Mediterranean areas of Iberia, including Catalonia, were probably cut off from the Cantabrian coast, so they probably did not participate in the repopulation of north-west Europe. As I see it, there is an axis dividing the Iberian Peninsula into two distinct prehistoric areas: on the one hand, the Atlantic Façade, comprising Portugal and some regions of northern and central Spain; on the other, a Mediterranean Façade, connected with southern France and Italy. This division, caused by climatic and geographic features, is also reflected in the distribution of languages in prehistory: Celtic in the west and Iberian on the Mediterranean, as can be seen in the map of the left (source: Arkeotavira). How old are these linguistic borders? What were the languages spoken by those people who repopulated the British Isles and other northern regions from the Franco-Iberian refuge? These are difficult questions to answer. Geographic features are an important factor in population movements, as they define the possible routes of communication and the chances for interaction. This can clearly be seen during the LGM, the most hostile environment that can be imagined for human populations in Europe, but also in other periods, with milder climatic conditions.

In some previous posts (e.g. here) I have suggested some possible scenarios for the languages of the Iberian Peninsula in pre-Roman times. One of the hypotheses, as stated by Xaverio Ballester and other authors, is that the speakers of Iberian languages arrived at a later period, settling over a territory where IE (possibly Italid) languages were spoken. But where did these Iberian-speakers come from? A possible candidate is Aquitaine, in south-west France, as some parallels can de drawn between the ancient languages of the Aquitani and Iberian. It has also been argued that Iberian is connected with Basque, and this idea was actually quite popular in the 20th century, leading to some simplistic equations of Basque and Iberian which were more enthusiastic than scientifically sound. In any case, it is reasonable to see some possible links between the languages of the Basques, the Aquitani and the Iberians. Now, what is the possible geographic connection between these territories? If we look at the first map again, we find that there is actually a natural corridor uniting those areas: the Garonne River Valley, situated between the Pyrenees and the French Massif Central; at its centre, the city of Toulouse, a strategic point in this route. Was this natural corridor shut off during LGM? It would be interesting to know.

Whenever one attempts to make sense of the languages of western Europe, one is forced to face a familiar mystery: the presence of an unexpected non-IE linguistic isolate: Basque. And to make matters worse, the Basque-speaking area is actually at the heart of the Franco-Iberian LGM refugium. According to the German linguist Theo Vennemann, the people in the Franco-Iberian refugium spoke languages related to Basque, and they spread them through vast areas of western and northern Europe. These languages were later superseded by Indo-European (except of course in the Basque Country) and their traces, as Vasconic Substratum, can be found in the vocabulary of some European languages, including toponymical terms. Vennemann's theory has not been accepted in general, and I personally think it's not tenable (I'll discuss it in a future post). However, it presents a coherent explanation in terms of prehistoric events. Now, is there an alternative explanation? Let's try.

The question is: why would a language, in this case Basque, be excluded from the opportunity of expanding to a new territory, in this case post-Ice-Age northern Europe, when the opportunity arose? First, it must be said that, in theory, there's no reason to believe that Basque was spoken in that area at such an early age (the Mesolithic), but in any case, for the purposes of this investigation, let's assume that this was the case. The Basque country of today occupies the coastal corner of land that connects Spain and France. At first sight, this would have been the natural route for any population transfer from the LGM refugium to the north. However, let's remember that at that precise moment the coastal line was different from the one we have today; the sea level was much lower, and the lowlands extended well into the Antlantic. At least in theory, it is possible that some populations along the Cantabrian coast, speakers of a non-Basque language, moved to the north, bypassing the highland areas where Basque-related languages were spoken and actually impeding any possible expansion of this language group into the new horizon created by the receding ice. And it can also be argued that these 'opportunists' from the Cantabrian refuge were speakers of some form of Indo-European, but that's of course a different discussion. In any case, is it reasonable to suppose that the Basque-speaking population just missed the chance for expansion? The situation is not impossible in itself. To illustrate the point, I will provide an example which bears some distant resemblance: the conquest and colonization of America.

The discovery of America opened a new horizon for European populations and languages, but who took the chance? Obviously, there is a geographic factor in this: it was the areas around the Atlantic that were involved in the whole process. First the Spanish and the Portuguese, then the English, the French and the Dutch. Let's take a look at the Spanish expansion: who took part in it? Basically, it involved people from the west side of the axis (see above), mainly from areas such as Extremadura or Andalusia. There was little or no involvement of people from the Mediteranean coast in the whole event. Consequently their language (Catalan) played no role in the story. This can be explained in geographic terms but also, more importantly, in socio-economic terms: the eastern regions of Spain are in a different context, one that connects them to other Mediterranean territories. In addition, the discovery of America coincided with a time of decadence for the Catalan language, with Spanish as the language of the new emerging power.

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.

9 July 2009

Origins of the Etruscans

In 2004, a group of Italian researchers published an article with an innovative type of research about the origins of the Etruscans (see Vernesi et al, 2004). They analyzed the genetic components of bones found in Etruscan tombs and compared them with the genes of modern populations of the same areas. They found out that there were significant differences between these two populations, with a clear pattern of discontinuity which is by no means easy to explain. Suggesting a process of massive migration or population shift does not seem in accordance with archaeological evidence. The authors suggest a more plausible explanation (p. 702): “Those tombs belong [to] the social elite (...) and so the individuals we studied may represent a specific social group, the upper class. We do not know whether that group differed genetically from the rest of the population, which might be the case when a foreign elite imposes its rule, and often its language, over a region”. According to the authors, the genetic components of ancient Etruscans show similarities with those found in Near East populations, which makes them think of a possible gene flow from that area, but the results are not conclusive. In any case, the publication of this article triggered a series of research projects that have shed new light into the matter (for a complete view of the main developments you can take a look at Dieneke’s Anthropology Blog; e.g. this post). In a very recent research work (Guimaraes et al, 2009; see abstract here), the authors compared the genetic materials of ancient Etruscans, Medieval and present-day Tuscans. They found out that there is continuity between Medieval and modern populations, as expected, but not with ancient Etruscans.

I suppose in the next few years there will be more research in this area, especially with the development of newer, more accurate ways of analysing old genetic material. Although it is very difficult to interpret these data and establish possible affiliations between the various populations, it seems that the DNA analyses suggest, at least, a clear pattern of discontinuity in Etruria/Tuscany. Traditionally, the Etruscans (speakers of a non-IE language) have been seen as an autochthonous population of the Italian Peninsula, older than the Italic populations (speakers of IE languages). This view, based on a Roman-centred perspective, has rarely been challenged or tested, and has been held as undisputed truth for centuries. Now, with the development of new tools for research, it seems that the picture is exactly the opposite: it was the Etruscans, as an intrusive elite, that arrived later.

Now, the logical question is: where did they come from? Some connections with Turkish or eastern Mediterranean populations have been suggested from ther genetic data, but they don’t seem to be conclusive. I suppose there will be some more research on this, and not only in the field of genetics: it is necessary to compare the genetic data with the evidence found by archaeologists and linguists. Let’s take Mario Alinei for example. His idea that the Etruscans descended from ancient Hungarians is based on archaeological and linguistic evidence. Maybe he's right, or maybe not, but in any case his proposals are coherent (see this post for more details). One of his assumptions, namely the late arrival of the Etruscans, seems to be corroborated by independent research, as we have seen; his proposals about the chronology of Hungarian prehistory and the linguistic parallelisms between Etruscan and Hungarian are much more speculative and still need to be tested. A curious coincidence is that, according to Alinei, there are numerous Turkic elements in both the Hungarian and Etruscan languages, which he interprets in the context of Ugric-Altaic contacts in the 4th and 3rd millennia BC. I remembered this when I read about the ‘Turkish’ and eastern Mediterranean component in the Etruscan genetic material. It is obvious that the terms ‘Turkic’ and ‘Turkish’ refer to completely different concepts: a language family in Asia (Turkic) and a modern country where a Turkic language is spoken (Turkey). Maybe it’s just a coincidence, but who knows? I’m sure geneticists will come up with new, sometimes surprising results.

- Guimaraes et al (2009). Genealogical discontinuities among Etruscan, Medieval and contemporary Tuscans.
MBE, Advanced Access published on-line. (Abstract).
- Vernesi et al (2004). The Etruscans: a population-genetic study.
AJHG 74: 694-704.

Images (from top to bottom): 1. Sarcophagus of the Bride and Bridegrrom, 6th c. BC. Museo Etrusco di Villa Giulia, Rome; 2. Map of the Etruscan territories in ancient times; 3. Etruscan Musicians. From a tomb in Tarquinia, 5th c. BC.
Last Edit: 20 July 2009

13 June 2009

Language continuity in Europe (III): Ireland

Who brought Celtic languages to Ireland? And when? - It seems that there is no easy answer to these questions.

In general, islands are a good place to study population and language evolution, because they offer a more limited range of variation and better chances for establishing the chronology of events than in continental land. The British Isles are not an exception. In fact, there’s a detail that makes this area even more interesting for the researcher: due to their location in the northern Atlantic, the British Isles have been greatly affected by major climatic changes, especially glaciations. It is supposed, for example, that by the time of the Late Glacial Maximum (LGM), i.e. the coldest period of the last ice age (about 22,000 to 17,000 years BP), the British Island became a frozen desert, with no possibilities for human life. The re-population of the British Isles started from zero when the ice started to recede.

In the comments to a recent post in this blog we had an interesting discussion about the Celts. One of the commentators, Ian, suggested a book about this topic: Stephen Oppenheimer’s The Origins of the British (see below for full bibliographic details). I had never heard about this book before, and I found it interesting so I ordered it on the Internet and a week later I had it in my hands. Reading it was just a matter of days. No doubt about it, this is the ‘21st-century’ at work! Speed and availability. Ideal for inquiring minds.

In his book, Stephen Oppenheimer offers a detailed analysis of the history of human populations in the British Isles. Being a geneticist, he focuses primarily on the genetic material of these populations, combining it with other sorts of evidence, e.g. from archaeology or history texts. His research is quite comprehensive: he analyses and discusses the results obtained by previous authors, e.g. Sykes and Richards, and offers new, generally more accurate explanations for the history of British gene clusters. I had never seen such a complete and detailed account of western European genetic history, and, not having yet read any review of this book by other geneticists, I am not in a position to say if all the details of Oppenheimer’s theory are acceptable or not. In any case, I have the impression that the overall picture offered in this book is coherent and logical, and is bound to become a reference point in any future study of western European prehistory. Now, what is this ‘overall picture’? It is difficult to summarize Oppenheimer’s book in just one post, and I suppose I’ll be talking about it in future occasions. There is an article by Oppenheimer (published in Prospect), where you can find some of the main points in his theory.

The re-colonization of the British Isles took several steps, starting about 16,000 years ago after the LGM. The first colonizers came from the Franco-Spanish refuge, an area in northern Iberia and southwestern France where human life had not been interrupted by the ice. This Iberian gene flow is by far the most important element in the genetic components of the populations in the British Isles, especially in Ireland, Wales, Cornwall and other western areas. At about 12,300 BP there was another glacial period, called Younger Dryas, which also had an impact on this area. It is thought, however, that human population did not disappear from the British Isles in the Younger Dryas, even though there was a significant demographic drop. The Younger Dryas was much shorter than the LGM: by 11,000 BP the climate started to become much milder, like the one we have today. This period, known as Mesolithic, saw a new process of colonization from the continent, which two main lines: from Iberia and from northwestern Europe. This double migration path is actually a recurrent pattern in the prehistory of the British Isles, which is repeated in later times (Neolithic, Bronze Age, Iron Age). According to Oppenheimer, this pattern of migration set the basis for the separation between Celtic and Germanic areas in the British Isles. In other words, the boundaries between these two areas are not the consequence of recent historical events, like the Anglo-Saxon invasion, but were established in a process that started in the Late Upper Paleolithic, after the LGM. Basically speaking, what we have here is a pattern of continuity of human populations. The genetic input from the earlier times (Paleolithic or Mesolithic) is the most relevant component in the genetic material found in populations of that area today. The contribution of later migrations, e.g. in the Neolithic, is considerably lower, which means that the expansion of agriculture and metallurgy was not the consequence of massive migration, but a local development. This is especially true in the case of Ireland, as we will see.

It is not clear if Ireland was re-colonized by humans immediately after the LGM, but there are some indications pointing in this direction. There is clear evidence, however, of human migration into Ireland during the Mesolithic, mainly from Iberia. On the left you can see a map from Oppenheimer’s web-page, with the distribution of one of the gene clusters from Iberia, following a typical pattern. The impact of later migrations into Ireland is generally considered low, in comparison with eastern Britain, which was under the influence of migrations from northwestern Europe. According to Oppenheimer, intrusive lines in the Neolithic account for 6-9 % of all Irish genes. This doesn’t mean that Ireland was isolated from the rest of the world in prehistory; in fact there were strong links between Ireland and other Atlantic European areas, as shown by Cunliffe and other authors who talk about the ‘Atlantic Façade’. But it is clear that the Neolithic and other later prehistoric periods did not involve a relevant population input in Ireland. Now, let’s go back to the initial question of this blog: Who brought Celtic languages to Ireland? And when? – There are several possibilities: in the Mesolithic, as the Continuity Theory proposes; in the Neolithic (Colin Renfrew’s theory); or in the Iron Age, as some people still think. - At this point, Oppenheimer asks a couple of interesting questions (p. 246): “how could a new language arrive during the Neolithic without people? (...) Was 6% invasion enough to change culture and language?” For him, the possibility of a Paleolithic or Mesolithic origin of Celtic languages in Ireland is “unlikely” (p. 222), but not impossible. It is clear that the door is open for new research on the languages and populations of the British Isles, and of Ireland in particular, with new perspectives and new tools that were not available just a few decades ago. And it is also becoming quite obvious that the Central-European theory of Celtic origins, which puts them in connection with the Halstatt or the La Tène Iron-Age cultures of the first millennium BC, is quite unacceptable.

- Oppenheimer, Stephen (2007). Origins of the British. London: Constable and Robinson [first edition, hardcover: 2006, London: Constable and Robinson].

25 April 2009

Populations and languages: the Strait of Gibraltar

Many years ago I made a trip to Gibraltar. At that time I was a post-graduate student at the University of Valencia, and one of the courses I took was about dialectology and sociolinguistics. We had to do some research as the final assignment of the course and in my group we decided to go to Gibraltar to do some field-work about the linguistic situation of this peculiar place. We spent three days there, with our questionnaires and interviews, and we also had time to do some sightseeing: we walked around the city, we saw the famous monkeys and we finally climbed the Rock, from where we had some spectacular views of both Spain and the African coast, which is a mere 14 km away. We can imagine that, throughout history and prehistory, many humans living on either side of the Strait must have felt curious to know about the land that they could see across the water, and this curiosity could have led to a significant movement of human populations in both directions.
The surprising fact, however, is that the Strait of Gibraltar has been a barrier for human migration in all ages, especially in prehistory. The main reason for this is geological: the Strait of Gibraltar has remained as it is now for the last 5 million years, even at the various glacial ages, where the sea level lowered significantly all over the world. We also have other types of evidence, e.g. the archaeological record, but the most important confirmation has come from population genetics. I recently read an interesting article about this subject: Bosch et al, 2001, High-Resolution Analysis of Human Y-Chromosome Variation Shows a Sharp Discontinuity and Limited Gene Flow between Northwestern Africa and the Iberian Peninsula, American Journal of Human Genetics, 68:1019-1029). In this article, the authors analysed the genetic components of various populations in Spain and Morocco, combined with other evidence from archaeology and history, and reached a series of interesting conclusions. It seems for example that in both cases, the populations of today are mostly the descendants of the people who lived in these areas in the Paleolithic, with a minor impact of migration from the Middle East, probably associated with Neolithic expansion. On the other hand, the genetic components of Iberian and NW African populations show that they come from different origins. Human settlement in Iberia is connected with the expansion of modern humans into Europe from Eurasia or Anatolia, whereas the population of NW Africa is mostly connected with components that originated in the African continent. The gene flow across the Strait of Gibraltar is not considered relevant; it can be estimated at about 5%, and it could, at least partially, show the traces of some recent historical phenomena, like the expansion of the Roman Empire or the Arabic conquest of Iberia. There’s no doubt that the Strait of Gibraltar, as a natural barrier, has played a decisive role in the distribution of human populations, both for modern humans and for older types of hominids. Instead of crossing the 14 km stretch of water that separates Africa from Europe, it took humans a few thousand years to go all the way to the Middle East and eastern Europe until they reached the Iberian Peninsula. This is what I would call a ‘Grand Tour’.

Now, what are the linguistic consequences of all this? Is there also a linguistic barrier as well? Has this language barrier existed from prehistoric times? In a previous post I wrote about the expansion of Arabic as a consequence of the Islamic Empire. The main conclusion I reached was that Arabic dialects are spoken today only in areas where other Afro-Asiatic languages (formerly known as Hamito-Semitic) were already spoken before the arrival of the Arabs, and not in areas where there were other types of languages, e.g. in Persia or Iberia. I’m not sure if anyone had realised this simple fact before, but it looks quite clear in my opinion. The important factor here is affinity. The language of the conquerors (in this case Arabic) has a varying degree of influence on the languages of the conquered depending on the affinity between them. When the Arabs arrived in northern Africa they found Berber-speaking populations, and Berber languages belong to the Afro-Asiatic group. The subsequent process of hybridization led to the linguistic situation that we find in the area today, with a series of dialects which are considered regional variations of Arabic (with the exception of the areas where Berber languages have survived until today). What about Iberia? The languages spoken in this territory were quite different from Arabic; they were connected with Latin, an Indo-European language belonging to the Italic group. The Islamic conquest brought about a process of hybridization, with a significant exchange of linguistic (mainly lexical) material in both directions, as can be seen in the vocabulary of Spanish, Portuguese and other Ibero-Romance languages, and also in many features of the Hispano-Arabic dialect. However, Arabic and Romance languages were always perceived as something different. There were not enough opportunities for hybridization to produce significant hybrids between them; people spoke one of the languages, or both, but not a mixture of them (except perhaps in some local, pidgin-like cases). Another example of the importance of affinity in situations of language contact can be seen in the Roman conquest. The influence of the Romans was linguistically relevant in the Iberian Peninsula, where there was already a background of Indo-European languages, whereas it was rather insignificant in northern Africa, with no Indo-European background (see this post for more details and some maps).

It seems therefore that the population/language distribution in NW Africa and Iberia corresponds to a pattern that dates back to Paleolithic times, when modern humans arrived in these areas via different routes. The Strait of Gibraltar, as a natural barrier, was the main factor behind the whole process, limiting the possibilities of genetic or cultural exchange. Later developments, associated with the rise and fall of empires and the expansion of religions, were not strong enough to change the overall picture.

Notes on the illustrations:
- First picture: The Strait of Gibraltar from Spain. Source: OjoDigital (here).
- Second picture: The Strait of Gibraltar and the Alboran Sea. Source: NASA (here).

29 June 2008

Out of Africa

The only massive human migration in pre-history about which there is no doubt is the one that took modern humans from Africa to the rest of the world. It is estimated that Homo Sapiens Sapiens appeared as a new hominid species somewhere in Central Africa approximately 200,000 years ago, and it started to spread around 100,000 years later. Nowadays, this theory, called the single-origin-hypothesis, or simply the Out of Africa model, is generally accepted among paleoanthropologists and in the scientific community in general. The alternative view, known as the multi-regional hypothesis, has fallen into oblivion, especially after strong evidence from genetics started to confirm the single origin of the human species in Africa. The study of the genes in our DNA can be used as a means of establishing the evolution and main parameters of human populations. The first research in this area was carried out in the 1960s by the Italian geneticist Luigi Luca Cavalli-Sforza. In the last decades new techniques for DNA analysis have been developed and many scientists have continued to provide new results, which confirm and refine the monogenetic theory and help to open new research horizons. An example of this type of research can be seen in the following article: UNDERHILL, P.A. et al (2001), The phylogeography of Y chromosome binary haplotypes and the origins of modern human populations. Annals of Human Genetics, Volume 65, Issue 1, Page 43-62.

The image below is a map of the world which shows the Out of Africa expansion of H. Sapiens at its various stages:

(click here for a larger image and full details).
This all comes to confirm a very simple fact: ALL HUMANS COME FROM AFRICA, a sentence that racists and xenophobes should be reminded of from time to time.

Now, what about language?

In the scientific community there is no general agreement about which human or hominid species was the first one with a speech capacity. Was it a specific development or a mutation of H. Sapiens, or did modern humans just continue a pre-existing speech capacity of H. Erectus or other hominid species? On the other hand, it is not clear whether human language originated at a single location (monogenetic hypothesis) or more or less simultaneously in more than one place (polygenetic hypothesis). There’s a variety of proposals about these issues and a huge amount of research is being conducted involving archaeology, linguistics, paleoanthropology, genetics, neuro-science and other scientific disciplines. The most recent developments in this research seem to point in the direction of monogenesis. According to this view, which I share, the human language capacity was born with Homo Sapiens in Africa and it started to develop about 200,000 years before present. We know nothing about the possible ‘languages’ of the other hominid species (H. Erectus, H. Sapiens Neardentalensis, etc.), and we can only try to guess what kind of relationship there was between their communicative systems and the language of H. Sapiens Sapiens. But as I said, there’s strong evidence suggesting that human language as we know it was born as an innovation of the only hominid species that has survived until today: ours.

The emergence and expansion of the various language families (Nilo-Saharan, Altaic, Sino-Tibetan, Indo-European, etc.) must be seen in the context of the Out of Africa migration of humans, that is, a process which began around 100,000 years ago. There is no evidence suggesting any other massive, transcontinental migration of humans at a later stage in pre-history, for example in Neolithic times. Traditional chronologies, like the one which sees the expansion of Proto-Indo-European in approximately 3,500 BC., are no longer tenable. They are based on wrong assumptions about language change and archaeology. Amazingly, this traditional chronology is still accepted in mainstream (historical) linguistics.

Further reading:
- BALLESTER, Xaverio (2002). Las Primeras Palabras de la Humanidad. Ediciones Tilde, Valencia.
- CHRISTIANSEN, Morten and KIRBY, Simon, eds. (2003). Language Evolution. OUP.
- SYKES, Bryan (2001). The Seven Daughters of Eve. W. W. Norton and Company.