Agricultural History Review, Volume 52 Part 2 (2004), p. 224

Prehistory is a profoundly geographical discipline. Prehistoric processes not only occurred over very long spans of time but over large areas. Innovations, such as agriculture, emerged in specific regions at particular times and then spread outward. Language families also spread widely, such that many of the world’s languages can be shown to have common roots. The human genetic heritage also has a geographical component, for it is clear that even after the initial dispersal of humans from Africa throughout the Old World, there were additional diasporas to the New World, Oceania, history review andAustralia, and even afterward there were more movements on a continental and subcontinental scale.

Sometimes the evidence for these movements of crops, languages, genes, and people converges, particularly during the last 10,000 years. In particular, the hypothesis has been advanced that the dispersals of several principal language families are correlated with the expansion of farming, especially when farming has been spread through the movement of people. When people move, they take their genes with them, which is where the genetic evidence comes into play. This volume contains 36 papers that emerged from a conference at the McDonald Institute in Cambridge that explore and assess this convergence of evidence. In addition to methodological and theoretical overviews, the volume has a global scope, including papers on Europe, the near east, south and east Asia, Oceania, and the new world.

The farming/language dispersal hypothesis is summarized by Renfrew as follows: the current distribution of some of the world’s largest language families (e.g. Niger-Kordofanian that includes Bantu, Austronesian, Indo-European, and Afro-Asiatic) is due to the demographic and cultural processes that accompanied the dispersal of the practice of food production from the core areas in which animals and plants were first domesticated. Renfrew first floated the idea in 1987 with specific regard to the spread of the Indo-European language family, which he argued occurred from Anatolia with the spread of agriculture into other parts of Eurasia. This flew in the face of conventional philological wisdom, which considered the dispersal to have occurred several millennia later and from a core area on the Eurasian steppes north of the Black and Caspian Seas. Subsequently, the hypothesis has been exported to other areas, with Bellwood being a very strong proponent based on his own research in the south-west Pacific area, and others, many of whom are contributors to this volume, embracing it to various degrees in other areas.

Although the hypothesis leaves open the possibility for language spread through the dispersal of agriculture by cultural diffusion to foragers who adopt domesticated plants, animals, and language, a major part of the discussion hinges on the concept introduced by Ammerman and Cavalli-Sforza of ‘demic diffusion’, thecumulative effect of long- and short-distance moves by farming peoples resulting in a ‘wave of advance’ of agricultural dispersal. This is where things get sticky, because archaeologists differ in the degree to which theybelieve that prehistoric people moved around. As a reaction to the traditional archaeological interpretation that change was the result of population movement, many archaeologists in the 1970s and 1980s embraced theassumption of in situ development until proven otherwise – except when patently impossible. Other archaeologists reasserted that migrations and colonizations may have played a significant role in prehistoric cultural change. This resulted in a degree of polarization between the ‘indigenists’ and ‘migrationists’.

As with any issue so polarized, the truth has to lie somewhere in the middle, and the growing body of genotype mapping offered hope for a resolution. For the most part, these data consisted of the mapping of genes in modern extant populations that were believed to have been in place for several millennia rather than the recovery of ancient DNA from archaeological skeletons, a technique still in need of methodological refinement. Over the last several decades, molecular biologists have built up an immense corpus of genetic data on ‘native’ populations from all continents. Inevitably, however, the genetic data often provide conflicting evidence for demic diffusion associated with the spread of agriculture.

Europe offers a particularly confounding example of the complexity of integrating archaeological and genetic evidence. In Europe, opposing clinal haplogroups 1 and 9 have been identified, discussed in detail by the biologist Matthew Hurles in his paper. Haplogroup 9 is considered to be the signal of immigrant farmers originating in Anatolia, and its frequency peters out dramatically along an axis from SE to NW, such that it is very scarce in the British Isles, although it even occurs at a low frequency in the Balkans and central Europe, presumably closer to its point of origin. Haplogroup 1, on the other hand, is believed to reflect the indigenous stock resident in Europe since the Palaeolithic, and it gives a very strong signal all along this axis and is overwhelmingly represented in north-western Europe. These data appear to contradict the notion of much population movement associated with the spread of agriculture, although fact that the ‘Anatolian’ strain is present at all says that some demic diffusion probably occurred.

Renfrew, in his introductory passage, addresses this problem and connects it to the question of language dispersals by presenting the hypothetical case in which farmers move into a geographically contiguous series of cells over a period of several centuries, intermingling to a relatively small degree with the indigenous population. By the end of several iterations of this process, the percentage of genes from the original ‘immigrant’ population that started it all could be vanishingly small, yet the resulting population after a millennium or more would be farmers speaking a tongue descended from that spoken by the original incoming farmers. The genetic signal can become attenuated while the cultural and linguistic signals are amplified.

The European case gives an example of how difficult it is to process these various streams of data. To carry the metaphor a bit further, certain regions such as island south-east Asia are full of static, whereas in other parts of the world, the data are so sparse that they are open to diametrically different interpretations. The key issue, put so well by Hurles, is ‘whether the archaeological record, which is so successful at allowing the reconstruction of ancient societies, identities and ways of life underrepresents to some degree the “compound interest” of inter-generation admixture that seems to be so critical in understanding the spatial and temporal distribution of genetic diversity’ (p.307).

As might be expected from this discussion of the complexity of the issues involved, this volume offers no breakthrough consensus. Some authors seek harmony among the competing categories of evidence, while others suggest that the hypothesis works in some places butnot in others. Such is the current state of the field. Another stream of data is entering to complicate things still further. The study of isotopes such as barium in prehistoric human bones and teeth, and the comparison to local background isotopic frequencies, is expected to provide evidence on which individuals were born and raised locally and which ones entered the area bearing isotopic signatures from elsewhere. Once the techniques for the extraction and analysis of ancient DNA mature, prehistoric skeletons will be able to speak with several voices about their lineage, which will be very important complements to the evidence from archaeology, linguistics, and population genetics.

In these days when the field known as anthropology is concerned with ‘globalization discourses’, the language/farming dispersal hypothesis really does address a real global anthropological problem. In many respects, the integration of archaeological, cultural, biological, and linguistic evidence is in the grand four-field tradition of true anthropological inquiry. The papers in this volume reflect this spirit of comparative analysis. Whether or not one agrees with their arguments or conclusions, one has to appreciate the scholarship that the papers in this volume demonstrate. None appear to have been dashed off in haste in order to gain a trip to a conference. Such a level of scholarship makes Examining the farming/language dispersal hypothesis an important contribution to an ongoing debate.