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The Younger Dryas Cold Event and
the Distribution of Nostratic Languages
by Jonathan Adams
Abstract
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.
Introduction
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.
References
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'.
Contact
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. (jonathan@elvis.esd.ornl.gov)
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