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The Younger Dryas Cold Event and the Distribution of Nostratic Languages
by Jonathan Adams

The Younger Dryas cold event (about 10,800-10,000 14C years ago) returned much of Europe and western Asia to dry, cold glacial conditions, apparently in several rapid cooling events. Following the Younger Dryas, warm, moist Holocene conditions seem to have returned rapidly all across the region, possibly over several decades. The climate transition into the Younger Dryas seems likely to have eliminated much of the previous late Palaeolithic population of northern and central Europe, and the return of warm conditions would have provided an opportunity for rapid population expansion to fill this gap.

It is possible that much of the range of the Indo-European languages was achieved by the spread of this 'sparse wave' of hunter-gatherers out of south-eastern Europe or Anatolia.

Other language groups, such as Basque, may have failed to expand out of Younger Dryas refugia in Southern Europe due to a slight delay that would have led to them being swamped by an exponentially growing population of Indo-European speaking hunter-gatherers.

This initial early Holocene spread of the Indo-European languages may have been followed by a period of relatively long-distance cultural and linguistic exchange (with possible spreading of innovations in the language, continually 'updating' aspects of the general substratum of Indo-European languages) by relatively mobile hunter-gatherer groups.

This hypothesis may be considered alongside Renfrew's 'farming wave' hypothesis and the earlier 'Battle-Ax' group of hypotheses, as another possible scenario to explain the wide spread of Indo-European languages by early historic times.

The question of how Indo-European family of languages came to occupy a broad swathe of Europe and western Asia has occupied the attention of scholars for centuries. Earlier hypotheses concentrated on migrations of war-like cultures (e.g. the 'Kurgan' or 'Battle-Axe' Culture) (Childe 1950, Gimbutas 1980) conquering relatively passive farming populations. More recently, Renfrew (1987) has suggested that the main event in the spread of the Western Branch of these languages was the initial spread of farming out of the Near East, providing a population 'wave' (due the increased carrying capacity of the farming lifeway) that swamped out the languages of hunter-gatherer groups, speaking non-Indo European languages, that had previously existed in the area. This idea has recieved some support from genetic evidence of a south-east to north-west gradient in gene marker frequencies across Europe (Cavalli-Sforza et al. 1994.), which has been taken to be the legacy of the 'farming wave' that spread out of Anatolia beginning around 9,000 BP. The genetic evidence from the 'farming wave' has been disputed (Ref.s), on the grounds that other (earlier or later) major population expansions could have followed the same track. Here we suggest that both a somewhat earlier wave of population out of the Near East may have carried Indo-European languages across much of Europe and part of the way eastward into central Asia.

The evidence of the Younger Dryas climate change and it relationship to human occupation
The Younger Dryas cold period was first noticed in the pollen records of NW Europe, but it has since been found to have been a major climate event across Europe, Eurasia, eastern North America, and possibly many other areas around the world (Starkel 1991, Jalut 1992, Velichko 1993). It followed a relatively warm (possibly warmer than present) and moist phase that began around 14,000 calendar years ago (13,000 radiocarbon years ago) (Velichko 1993). During this Late Glacial Interstadial phase, forest vegetation began to spread back across northern Europe and Siberia (Velichko 1993), and Late Palaeolithic humans were present in NW Europe at this time (ref.s).

The Younger Dryas seems to have begun in a rapid, stepwise manner (ref.), bringing about very dry, arctic climates all across temperate Europe and Siberia, and much drier than present semi-desert conditions across southern Europe and eastern Asia. The available evidence suggests a sudden ending, bringing about a transition to moist, temperate climates similar to the present in the space of several decades, with a slower response in terms of tree cover, taking more than a thousand years to regain the woodland cover lost during the Younger Dryas.

The 1,300-year Younger Dryas interval seems to be marked by a hiatus in human occupation of northern Europe, and its ending closely corresponds to the beginning of the Mesolithic in Europe (ref.s). It therefore seems likely that, as one might expect a priori, the sudden replacement of temperate climates by dry arctic climates led to elimination or out-migration of most of the population of northern Europe, and the confinement of settlement to parts of southern Europe where the climate remained moist enough to provide a continuing supply of wild food plants and animals. During the full-glacial period (30,000- 14,000 calendar years ago) it seems to have been the lower elevations of hilly areas in southern Europe at provided refugia to human populations. We should bear in mind, however, that the impact of the Younger Dryas on populations that had effectively lost many of their cultural adaptations during the preceeding 3,000 years of warm, moist climates, could have been very severe, and their population densities and ranges could have been more restricted during the Younger Dryas due to cultural maladaptation to the changed environment. In Asia Minor, it is becoming clear that the Younger Dryas could have had a major impact on the move towards a farming economy (Sherratt 1996).

A hunter-gatherer population wave as the carrier of Indo-European languages
The rapid amelioration of climate at the beginning of the Holocene would have created an opportunity for occupation of large areas of land. Most of Europe would have been now have returned to steppe or scrub-like vegetation, supporting populations of wild horses, sheep and other large animals, hazel and beech as a source of nuts (Huntley & Birks 1983), and possibly such food plants as wild barley and other grains in the steppic areas that remained predominant for several centuries following the start of the Holocene (Starkel 1991, Velichko 1993). The lack of cultural adaptations to a drastically different new climate and ecological regime, and the innate conservativeness of cultures surviving in the southern and south-eastern refugial areas (probably in mountainous foothills, as is argued above), may have led to delays in population movement out of the refugial areas. Any one group that acquired both the cultural habits that caused it to spread rapidly out of a refugium, and the technology to enable it to do so, would have experienced rapid exponential population growth in an environment free from competition by other hunter-gatherer groups. Such a group, spreading out northwards and westwards, and possibly eastwards as well, would make a disproportionate contribution to the genetic and linguistic legacy of Europe and parts of the Near East.

Other groups that were even a few centuries slower in expanding their range and populations would have become numerically dominated by the earlier colonists as they left their refugial homelands, given the likely exponential growth rate of each population. Even at the relatively low densities that hunter-gatherer populations would have been capable of achieving, competition or at least interaction between groups would eventually have become more frequent, with less abundant (non- Indo-European speaking) groups much more likely to lose their cultural and linguistic identity among a larger wave of Indo-European speakers. This scenario, of separate refugial populations which failed to expand fast enough to dominate linguistically, may explain the existence of the Basque (and possibly the Etruscan) language groups, as the 'potential' european dominants that narrowly failed to expand out before the Indo-European speakers became abundant. As the main Indo-European wave spread out in each direction, it can be expected to have 'gathered up' the genetic legacy of those (less abundant) populations it encountered along its way, as each of these began a slightly later spread out of southern refugia. This process of 'gathering up' may explain some of the current east-west and north-south genetic gradients which now exist in Europe, and some of the differences between the present-day branches of the Indo-European family of languages

Possible problems with the 'sparse wave' hypothesis for Indo-European language spread
It is in the nature of scenarios for linguistic origins that they are difficult to test. Each one must rest upon the ease with which it seems to fit observed facts. I do not claim that the hypothesis I have put forward here is any more plausible than the 'Battle-Axe' or 'Farming Wave' hypotheses, but it should at least be regarded alongside them as another possible scenario for the origins of the pattern of Indo-European languages. In my view the question of the processes of origin and spread of language groups is sufficiently interesting that it deserves careful, reasoned consideration on the basis of whatever information is actually available, even if this can never be said to arrive at actual certainty.

Various problems and complications with the 'sparse wave' hypothesis can be perceived. Estimates of the linguistic chronology of the Indo-European languages has been used to suggest that much of their common vocabulary has a more recent origin (about 7,000 years ago) (Swadesh 1972) than the early Holocene divergence that this 'sparse wave' hypothesis (and Renfrew's 'farming wave' hypothesis) would seem to require (about 10,000-11,000 years ago). However, one can make the point that linguistic dating is in itself potentially subject to great imprecision (Renfew 1987); and less than a factor of two error in the estimate of rate of divergence would be sufficient to push the divergence date back several thousand years from the mid Holocene to the earliest Holocene. Given that during this time there has been a drastic cultural change, to relatively sedentary Neolithic farming (in addition with lesser cultural changes in trade patterns and technology), all across the region and one must ask whether the linguistic chronology is accurate across such a change in group size, inter-group interaction and cultural complexity. One can suggest that for instance (M. Fraser pers. comm.) relatively mobile hunter-gatherer populations moving across large distances of the European continent would have retained their cultural and linguistic unity more readily than denser and more sedentary farming populations, where the opportunity for linguistic divergence between groups living in separate valleys or on different sides of a river would be substantially greater. It is difficult to say what effect such changes might have had on divergence rates, although they might possibly have been in the wrong direction for the 'sparse wave' hypothesis to be supported.

A second perceived problem is the difficulty of showing that that there were actually any large changes in population distribution during and after the Younger Dryas phase. Late glacial (14,000-11,000 y.a.) occupation of most of Europe is well demonstrated. There is only a small amount of information (discussed above) to suggest depopulation during this phase, but this may be because no-one has specifically looked for it. A priori, the rapid onset of severe aridity and lower temperatures of the Younger Dryas event would be expected to result in a major reduction in population densities across most of Europe and the near east. The rapid transition to warm interglacial Holocene conditions appears well established from both ice-core and terrestrial environmental evidence, and the rapid appearance of the Mesolithic culture throughout Europe is perhaps evidence of the relative population expansion which occurred with the return to interglacial conditions.

In summary, the initial very early Holocene spread of the Indo-European languages may have been followed by a relatively long period of long-distance cultural exchange (with possible spreading of innovations in the language, continually 'updating' the general substratum of Indo-European languages, whilst allowing for some regional divergences) by relatively mobile hunter-gatherer groups.

Multiple hypotheses of Indo-European spread
The three hypotheses for Indo-European origins (the 'sparse wave' proposed here, the 'farming wave' of Renfrew, and the 'battle-ax' group of hypotheses) are not necessarily mutually exclusive. For example, agriculture was already present in Anatolia during the Younger Dryas, and the 'wave' of hunter gatherers expanding out of this area might have included some sub-groups who had at some stage been engaged in agricultural activities; each process might have contributed at some stage and to some extent to the spreading and modernization of this language group.

Modifying the view of Sherratt (1996), it is possible that after a 'seed-bed' of the Indo-European languages was established across Europe and parts of western Asia in the early Holocene, continual cultural exchange and migration (e.g. interaction between hunter-gatherer groups, and later the spread of farming, followed by the 'battle-ax' migrations) tended to maintain and continually reinforce the recognizable affinity of the languages within this group.

Childe V.G. (1950), Prehistoric Migrations in Europe, Olso, Aschehoug.

Cavalli-Sforza L.L., Paolo Menozzi, Alberto Piazza, "The History and Geography of Human Genes", 1994, Princeton University Press.

Gimbutas M. (1980). The Kurgan wave migration (c. 3400-3200 B.C.) into Europe and the following transformation of culture. Journal of Near Eastern Studies. v.8 p.273-315.

Huntley B. & Birks H.J.B. (1983). An Atlas of Past and Present Pollen Maps for Europe: 0-13,000 years ago. Cambridge University Press, Cambridge.

Jalut G., Andrieu V., Delibrias G., Fontugne M. & Pages P. (1988). Palaeoenvironment of the Valley of Ossau (western French Pyrennes) during the last 27,000 years. Pollen et Spores v.XXX p.357-394.

Landmann, G., Reimer, A. and Kempe, S. (1996) Climatically induced lake-level changes at Lake Van, Turkey during the Pleistocene/Holocene transition. Global Biogeochemical Cycles V. 10, p. 797-808.

Renfrew C., "Archaeology and Language" (1987), Cambridge University Press.

Renfrew C. (1992), "The Emerging Synthesis" in Man, v.27 p.445-478.

Starkel L. (1991). Environmental changes at the Younger Dryas - Preboreal Transition and during the early Holocene: some distinctive aspects in central Europe. The Holocene v.1 p.234-242.

Swadesh M. (1972). The Origin and Diversification of Language. (Ed; J. Sherzer).

Velichko A.A. (1993). Evolution of Landscapes and Climates of Northern Eurasia. Late Pleistocene-Holocene elements of prognosis. Vol.2 Moscow 'Nauke'.

Note: This is a VERY rough draft for a paper I'm about to send into an archaeological journal. I'd be grateful for your comments and suggestions. I know you're not the type to indulge in plagarism, so I'm trusting you to see it (and anyway, lots of people have read the thing already). Thanks for your time and your comments! Jonathan

Anything missing? Anything incorrect? Don't suffer in silence - let me know and I'll change it. (