Limiting factors on early modern human dispersals: The human biogeography of late Pleniglacial Europe

Quaternary International 201 (2009) 77–85

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Limiting factors on early modern human dispersals: The human biogeography of late Pleniglacial Europe Alexander Verpoorte Faculty of Archaeology, Leiden University, P.O. Box 9515, 2300 RA Leiden, The Netherlands

a r t i c l e i n f o

a b s t r a c t

Article history: Available online 30 July 2008

Modern humans can be described as a colonizing species expanding its range from pole to pole in the course of the Holocene. The range shifts during the Late Pleniglacial in Europe form a case study in the limiting factors of early modern human colonizing behaviour. The paper provides an overview of the settlement history of Late Pleniglacial Europe (29–12.4 ka BP). The patterns of presence and absence are described in terms of biogeographical processes of abandonment, stasis and expansion. These trajectories differ from region to region, probably in response to climatic change. I explore the relationship between climate change and settlement history by focusing on the role of herbivore diversity. Patterning in herbivore diversity in relation to plant abundance and quality is proposed as an important factor in determining long-term settlement patterns in Late Pleniglacial Europe. Ó 2008 Elsevier Ltd and INQUA. All rights reserved.

1. Introduction In the course of their evolution, modern humans have colonized the entire planet from pole to pole. Not only anatomical adaptations but also changes in behaviour made modern humans able to colonize a wide variety of environments. These behavioural changes concern an increase in the range and intensity of social interaction and the complexity of spatial organization. Continental colonization and major range extension are even proposed as measures and indicators of modern behaviour itself, because colonization is ‘‘a social process, aided by technology and tempered by climate’’ (Gamble, 1994: 88). In line with the metaphor of ‘Out-of-Africa’, archaeology has emphasized the study of the timing, process, pattern, tempo and archaeological signature of colonizations (e.g. Kelly and Todd, 1988; Gamble, 1993; Housley et al., 1997; Davies, 2001; Rockman and Steele, 2003). Less attention has been paid to processes of abandonment and unsuccessful colonization attempts by modern humans. These issues are equally important because they concern the limits and constraints on human adaptations. One question for which this issue is important is the proposed difference between Neanderthals and early modern humans in the ability to colonize environments (Gamble, 1993, 1994). The settlement history of Pleniglacial Europe provides a case study for investigating the constraints on an early modern human hunter–gatherer adaptation. With the onset of the Last Glacial Maximum, humans retreated from the northern latitudes to more

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southern areas. The early modern humans failed to maintain themselves in large parts of Europe. Only with the climatic amelioration towards the Late Glacial did human populations resettle in the northern latitudes. Since the overview of the human world at 18,000 BP over a decade ago (Soffer and Gamble, 1990), new data have accumulated and chronological control has increased. The main aim of this paper is to present a revised overview of large-scale patterns in settlement history. The focus of this paper is on the environmental limits for early modern human hunter–gatherer adaptations. I pay attention to the abandonment process and regional differences in the archaeological record for the refuge period. I explore a model of herbivore diversity as a possible clue to explain these patterns. The study region is delimited in the west by the Atlantic Ocean, in the south by the Pyrenees, Alps, Dinaric Alps, the Lower Danube and the Black Sea, in the east by the Ural mountain range and in the north by the Norwegian and Barents Seas. The time period under consideration is roughly 29–12.4 ka BP (uncalibrated). 2. Data and biases 2.1. Data The reconstruction of settlement history is based on evidence for the presence of early modern humans. The data concern archaeological sites and human remains. The total number of data points is more than 400. Not all known sites are included in the database. Sites have been selected for their chronological control and geographical location with regard to northern limits of settlement. This means that there are many more data points for

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e.g. southwestern France but their information does not add much to the overall picture of settlement history. Dating of the sites and human remains is based primarily on 14C dating added with (bio)stratigraphic and typochronological observations. The data are organized in Excel datasheets and plotted using MapInfo software. The data – mainly sites with stone artefacts – are used as indicators for the presence of humans in the area for some time of the year at least. For our purpose no difference is made between permanent, year-round settlement and seasonal occupation of a site or region. 2.2. Time windows The time period is divided into three time windows. The basis of this division is the generalized pattern of global climate change recorded in the terrestrial loess and pollen sequences as well as deep sea sediments (CLIMAP) and polar ice (cf. Huijzer and Vandenberghe, 1998). The boundaries are located where there is a change in climate; the direction of climatic process is the same in the whole time window. The dates are given in 14C years. The time windows are 29–24, 24–17 and 17–12.4 ka (Table 1). The lower boundary of 29 ka is arbitrary and indicates the start of the Gravettian ‘culture’. Time window 1 forms the baseline for registering change during the Pleniglacial. The boundary of 24 ka is the onset of the Last Glacial Maximum, the boundary of MIS 2 and 3. Time window 2 is the downturn of climate. The boundary of 17 ka is the maximum extent of the Fennoscandian ice sheet and the temperature minimum. Time window 3 is the deglaciation period. The upper boundary of 12.4 ka is the start of the Bølling–Allerød interstadial complex. Time windows are used to accommodate the generally low resolution of the terrestrial record. All sites are attributed to one of these windows. Three levels of uncertainty are distinguished for the attribution of the sites to a time window: high certainty refers to reliable 14C dates supported by typochronological indicators and/or stratigraphic information, low certainty refers to contradictory lines of evidence and/or lack of good chronological information (no 14C dates, no clear typochronological indicators, no stratigraphy), medium certainty refers to limited and/or too general information on the chronology of a site. In addition, more detailed chronological information is used to describe the patterns within these time windows. The temporal resolution grades roughly from one to two millennia on the lower age range to less than half a millennium in the upper age range. 2.3. Bias Several biases influence the data. These are differences in research intensity and geological history. The information is not evenly distributed across space. The main problem in this respect is the relatively low research intensity in the area between Moscow and the Urals and in the mountainous area of the Balkans. In addition sites are not distributed evenly across geomorphologic

Table 1 Chronostratigraphy of the Late Weichselian. MIS Chronostratigraphy Major climate Time window of the Late characteristics (ka BP 14C years) Weichselian 12.4–10

2

17–12.4 24–17 29–24

3

Late Glacial Late Pleniglacial

Warming phase: Bølling–Allerød, Younger Dryas cold Deglaciation period: gradual ice retreat, high aridity Glaciation and maximum ice advance Interstadial complex: Denekamp–Stillfried B-Bryansk

zones. Most sites in Western and Central Europe are located in hilly and mountainous terrain, with caves and rock shelters. Most sites in Eastern Europe are located in zones where the loess belt is cut by rivers and dry valleys. The emphasis on particular site clusters such as Dolnı´ Veˇstonice in the Czech Republic and Kostienki in Russia, or on small micro-regions, such as the Perigord in France or the Swabian Jura in Germany does not form an obstacle for interpreting larger scale patterning. Instead these detailed records of microregions form the core data for patterning on a European scale. The geological bias concerns the sedimentation history of specific areas. The Holocene sediments in the Lower Rhine Basin and the Hungarian Basin cover earlier traces of occupation. Late Glacial cover sands on the northern plains may cover traces of Pleniglacial settlement. Loess was deposited mainly between 25 and 13 ka BP, potentially covering traces of occupation in the time window 29–24 ka BP. The extension of Alpine glaciers and the Fennoscandian ice sheet may have disturbed traces of occupation older than approx. 17 ka BP. The drowning of the North Sea basin and continental shelves makes these territories largely inaccessible for archaeological survey. The geological history of sedimentation and erosion creates a bias increasing with time. The older the traces, the more geological processes have been at work. Despite these biases in the data, their influence is accountable and/or limited on the large European scale. The main problem is that the absence of evidence cannot be taken as evidence of absence in any straightforward manner. It is difficult to prove that absence of evidence is due to absence of humans rather than lack of research and/or geological processes. The position taken here is generally that the absence of evidence indicates the absence of humans until evidence of the presence of humans is found. I will first discuss the spatial patterning within the three time windows and then explore main patterns in the data for three large areas: Western, Central and Eastern Europe. 3. General patterns in settlement history All data are attributed to one of the three time windows. Each time window will be discussed. 3.1. Time window 29–24 ka BP (Fig. 1) The period is best known from sequences in southern France (e.g. Abri Pataud) and open-air sites in the Czech Republic (Prˇedmostı´, Dolnı´ Veˇstonice and Pavlov), Austria (Willendorf), Russia (Kostienki) and the Ukraine (Molodova). From a cultural-historical point of view the sites of this time window are assigned to (regional and temporal varieties) of the Gravettian. Time window 1 includes 80 sites for a period of 5000 14C years (16 sites/1000 14C years). The attribution of sites to this period is generally fairly certain, meaning that the 14C dates are often matched by typological and/or stratigraphic observations (45% of high certainty, 35% of medium and 20% of low certainty). Settlement is widespread in Western Europe. The human burial in Paviland (South Wales, Great Britain) documents the northernmost occupation in Western Europe (latitude of almost 52 degrees). Direct dating of the human remains gave results of 25.8 and 26.3 ka BP (Aldhouse-Green and Pettitt, 1998). Gravettian sites are known from the Belgian Meuse Valley, the German Rhineland and the Upper Danube valley. The surface collection of Bilzingsleben (Germany) indicates some presence on the northern plain (Otte, 1981). It contains a number of Font Robert points indicating a date in time window 1, but no 14C dates are known. Lithic raw materials in the large open-air sites of Dolnı´ Veˇstonice and Pavlov indicate the exploitation of the moraines of southern Poland. Polish sites like Wojcice, Henrykow and possibly Oblazowa

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Fig. 1. Northern site distribution for time window 29–24 ka BP.

cave are attributed to this time window and indicate settlement of the loess area. The southern regions of Central Europe, the Balkans, have a very limited database. No sites are confidently dated between 27 and 21 ka BP in the Hungarian Basin. This absence may be an artefact of geology and research intensity. Data from open-air and cave sites document human presence in Romania and Bulgaria. Only a few Russian localities are dated between 29 and 24 ka BP. Sungir, north of Moscow, is one of the most northern locations (latitude of almost 58 degrees). Garchi I and possibly Medvezhya Cave indicate occupation at about 60 degrees north on the western edge of the Ural mountains (Pavlov and Indrelid, 2000). Also the more southern areas were exploited as indicated by sites in the Dniestr basin (Ukraine) and the Crimean peninsula. The scarcity of data in Eastern Europe is due to our focus on northern limits and probably also to loess deposition after this time window. A comparison with biomes reconstructed on the basis of floral and faunal evidence for the time period 33–24 ka shows that all biogeographical provinces (different varieties of steppic environments) were settled to some extent except the full forest tundra zone in the north (Markova et al., 2001, 2002; Simakova, 2001, pers. comm. 2003). 3.2. Time window 24–17 ka BP (Fig. 2) Time window 2 covers the downturn of climate with the extension of the Alpine and Fennoscandian ice sheets. Southern Scandinavia is still ice-free at the very beginning of this time window (Larsson, 2000). By the end of this period, the inland ice reached the line Berlin–Warsaw–Minsk, forming a wedge between east and west. Culture-historically this time window is rather complex. A gradual development of Gravettian industries characterizes Eastern Europe. Western Europe shows a sequence of Gravettian, Aurignacian V, Solutrean and Badegoulian (or Early Magdalenian). The Central European sequence is a sequence of Late Gravettian and an unclear entity with possible relations to an earlier Aurignacian, a variety of the Gravettian and/or the Badegoulian (Terberger and Street, 2002; Svoboda and Nova´k, 2004). Time window 2 includes 117 sites for a period of 7000 14C years (16.7 sites/1000 14C years). The certainty of age attribution is high (57%) or medium (38%). Only 5% of the sites have a questionable

attribution to this time window. The pattern is biased by a focus on the complex record for Central Europe. Many more sites in southwestern France are known to fit in this time window. Major changes take place in the distribution of human settlement at the onset of the second time window. It is a period of abandonment of areas and local extinction of populations. Northwestern Europe (Great Britain, Belgium and Northern France) is deserted. No sites are confidently dated between 24 and 13 ka in this area. The most northern Solutrean and Badegoulian sites (Beauregard, Saint-Sulpice-de-Favie`res, typologically attributed to ca. 21–17 ka BP) are located on the southern edge of the Paris Basin (Schmider, 1990). The end of the Gravettian in southern Germany is dated to 24 ka. No dates are available for the Rhineland, but a similar date of abandonment seems reasonable. Recent research in Western Germany indicates short-lived occupational episodes around 20–18 ka, with small sites such as Wiesbaden-Igstadt, Kastlho¨hle-Nord and Mittlere Klause (Street and Terberger, 1999, 2000; Terberger and Street, 2002). Eastern Central Europe is not deserted by 24 ka BP (Verpoorte, 2004). Sites dating to the period 24–20 ka BP are known from Southern Poland (Krakow), Bohemia (Lubna), Moravia (Petrˇkovice, Milovice), Slovakia and Austria (Langmannersdorf) (Verpoorte, 2002, 2003). In the period 20–17 ka BP the focus of settlement shifts to the Hungarian Basin and Lower Austria (the site of Grubgraben in the Kamp valley), south of the formerly occupied territories. Stra´nska´ ska´la (Moravia, Czech Republic) is one of the most northern localities. Some exploitation of southern Poland is suggested by data related to the procurement of lithic raw materials from the moraines. The database for the Balkans is very limited but suggests human occupation in the area during time window 2. The archaeological record of the Ukraine/Moldavia (e.g. Molodova V, Cosautsi) shows a continuity of occupation throughout the period 28–17 ka, with a possible break in the period 23–20 ka. Most sites with 14C dates from Eastern Europe are included in the database. Compared to time window 1, a large number of sites is known from the Russian Plain for this period. Well-known archaeological sites on the Russian Plain (main layers at Avdeevo and Kostienki) are dated to this time window. The northernmost site of Sungir, in use at the beginning of this period, was probably

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Fig. 2. Northern site distribution for time window 24–17 ka BP.

occupied only seasonally. Comparison with the biogeographical provinces based on floral evidence from the Russian Plain in this period suggests that only the full forest tundra and the semi-desert were not settled by humans (Simakova, 2001, pers.comm. 2003). Only one Uralian site, Bezimannii Cave at 57 degrees north, is assigned to this time window. Medvezhya Cave at 62 degrees north may fit in this time window as well, but its date is ambiguous (Pavlov and Indrelid, 2000). Possibly the northernmost areas on the western slopes of the Urals were deserted in this period.

3.3. Time window 17–12.4 ka BP (Fig. 3) The database for time window 3 consists of 99 sites covering 4600 14C years, that is 21.5 sites per 1000 14C years. Fewer sites are accurately dated (40%). Most age attributions are of medium certainty (48%), though that of several is questionable (12%). The time window 17–12.4 ka BP has the most complicated settlement record. It is divided into two periods. For the period 17–13.5 ka BP, the occupation of Europe is very sparse. After 13.5 ka BP, the northern regions are gradually recolonized. In culture-historical terms, occupational traces are assigned to the Middle and Late Magdalenian in the west and to evolved phases of the Gravettian in the east. Only three areas have a record of occupational continuity in this period north of the Mediterranean coasts (Iberian peninsula, Italy, Greece): Southern France and the Ukrainian/Russian Plain and the Middle/South Urals. Middle Magdalenian sites are restricted to the area south of the Paris Basin. One of the most northern sites is Arlay in the French Jura. In the Late Magdalenian the range is extended to include northern France and adjacent regions as well as higher altitudes in the Pyrenees and the Alps. Most sites on the Ukrainian/ Russian Plain are concentrated in the drainage basin of the Dnepr. Several large camps such as Mezhirich and Gontsy are dated to the short period of 14–15 ka BP. The Uralian sites contain small artefact assemblages. The character of settlement in this region is not well known. Other parts of Europe, including Central Europe and the Balkans, were largely deserted. The major range extension into these areas

took place after 13.5 ka, before the onset of the Bølling interstadial. Late Magdalenian occupation in Switzerland and Southern Germany is dated from ca. 13.5 ka onwards (Housley et al., 1997). Dating of cut-marked bones from the Belgian Ardennes indicates human occupation after 12.8 ka BP (Charles, 1996). Systematic dating of the recolonization of the British Isles (England) demonstrates the first human occupation after 12.8 ka BP (Barton and Dumont, 2000). First occupation of Northern Germany is probably dated to the start of the Bølling interstadial. Magdalenian occupation in eastern Central Europe (Poland, Czech Republic) also starts after 12.8 ka onwards (Zlaty kun; Svoboda et al., 2002). The earliest dates for the recolonization of the Hungarian Basin and the Balkans are about 13 ka BP. The cultural affiliations of these industries are usually sought in the Evolved Gravettian and Epigravettian on the Italian peninsula, Greece and Eastern Europe. The range extension in Eastern Europe after about 13.5 ka BP is not clear due to lack of data. The site of Pymva shor documents occupation within the polar circle by 12 ka BP (Pavlov and Indrelid, 2000). A few sites indicate some occupation in Central Europe in the period 17–13.5 BP (Verpoorte, 2004). Most important are Maszycka Cave (Poland) and Brno-Videnska street (Czech Republic), both dated to ca. 15–14 ka BP. Maszycka Cave contains the so-called ‘navettes’, otherwise only known from Middle Magdalenian sites in France (Koz1owski and Sachse-Koz1owska, 1993).

4. Regional trajectories in settlement history The settlement history of Pleniglacial Europe can be divided into three regional trajectories. The data from Western Europe (10 West–7 East) can be summarized as the following trajectory. - Initial occupation of the entire region up to a northern limit of approx. 52 N in Great Britain and 51 N in the Low Countries and Germany. - Retreat of occupation north of 49 N (Paris Basin) from 24 to ca. 13 ka. - Continuity of occupation south of 49 N (‘refuge area’).

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Fig. 3. Northern site distribution for time window 17–12.4 ka BP.

The trajectory for Central Europe including the Balkans (7 East– 28 East) can be summarized as follows. - Initial occupation of the entire region up to about 52 N (with the possible exception of the Hungarian Basin). - Retreat from the western part (Germany) by 24 ka. - Continuity of occupation in the eastern part until 17 ka with the focus shifting southward after 20 ka. - Retreat from the entire region by 17 ka. - Recolonization of Southern Germany after 13.5 ka and Poland/ Czech Republic after 12.8 ka. - Recolonization of the Hungarian Basin and Balkans after 13 ka. This trajectory is complicated by the presence of short occupational episodes: around 20–18 ka BP in the Rhineland and the Upper Danube region, and around 14–15 ka BP in Southern Poland and Moravia. Summarizing the Eastern European data (28 East–62 East), the trajectory for this large area of plains constitutes the following. - Occupational continuity for the entire period in the central part, the Urals and the Black Sea coastal region (including the Crimea). - Initial occupation up to 58 N on the plains and 62 N on the slopes of the Urals. - Gradual retreat from these northernmost latitudes after about 24/22 ka BP down to 55 N (plains) and 57 N (Urals). - Concentration of occupation between 17–13 ka, mainly in the drainage basin of the Dnepr and the Middle and Southern Urals. - Recolonization of other drainage basins and northern latitudes after 13 ka (polar circle by 12 ka BP). 5. Geographical processes: examples 5.1. Abandonment of Central Europe The data for eastern Central Europe allow us to reconstruct a sequence of abandonment stretching some 7000 14C years (24–17 ka BP) (Verpoorte, 2004). This sequence starts with

territorial expansion in the period 24–20 ka. Sites are smaller but cover a larger territory, from Bohemia and Southern Poland to Eastern Slovakia and Lower Austria. Mobility possibly increased and population density may have dropped. The territory expands from a rough estimate of 200,000 km2 to some 300,000 km2. This territorial expansion correlates with the horizon of single Venus-figurines in Central Europe (Willendorf II, Moravany, Petrˇkovice) (Svoboda et al., 1996) possibly related to information exchange (Gamble, 1994). In the period 20–17 ka, the main focus of settlement moved southward into the Hungarian Basin and Lower Austria. Sites are small and widely dispersed across the landscape. The mobility pattern changed from a more tethered nomadism with regularly visited areas (29–20 ka) to full nomadism with limited recurrent use of locations (20–17 ka). Northern areas were still exploited as shown by the occasional presence of South Polish flints, but use was probably shorter and less frequent. No figurines are known from this time period. The territory may have expanded beyond 300,000 km2. Finally, the local population became extinct by ca. 17 ka BP. The process of population decline is probably not constant and gradual. Simulations of population dynamics at different population densities suggest large fluctuations at low population densities (Boone, 2002). A brief shortfall in regional resources could easily cause a regional population crash. The process of abandonment in eastern Central Europe took a long time and the region was abandoned much later than western Central and northwestern Europe. The British Isles, the Belgian Ardennes and Southern Germany were abandoned by 24 ka BP. The archaeological record of these areas for the period 29–24 ka actually consists of only few traces of occupation. Refitting of stone artefacts between localities in Southern Germany suggests very brief settlement phases in this area. The record of northwestern Europe can be interpreted as traces of seasonal hunting and collecting trips far north of the main winter camps at lower latitudes (48–49 N) (Roebroeks, 2000). With animal prey densities lowering after 24 ka BP, these areas were abandoned because the costs of tracking and killing animal prey did no longer weigh up to the benefits. The faunal record of

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northwestern Europe is very poor indeed for the period ca. 24– 13 ka BP (e.g. Stuart, 1982). This is in general agreement with the characterization of the dry North Sea Basin as a polar desert based on the virtual absence of pollen data. 5.2. Signatures of the refuge areas The main refuge areas for the Pleniglacial are located in the Mediterranean Basin. North of the Mediterranean latitudes, only southwest France, the Ukrainian/Russian Plain and the Middle/ South Urals have traces of occupation throughout the Pleniglacial. The archaeology of these refuge areas shows considerable variation. In southwest France and Cantabria on the Iberian peninsula, site numbers increase with the Solutrean, but only relatively few localities are attributed to the Badegoulian. Relatively many sites are known for the Middle Magdalenian around 15–14 ka BP. The Italian record shows continuous occupation from at least 26 ka onwards, but site numbers are low after 20 ka and the archaeological record is poor in terms of burials, personal ornaments and art (Mussi, 2001). In Greece only a few sites are known for the period between 30 and 20 ka. More data are available after 20 ka, showing continuous occupation into the Late Palaeolithic (Perles, 2000). The data of the Ukrainian and Russian Plain indicate a number of localities between 24 and 13 ka BP in several drainage basins. An increase in site numbers is registered around 15–14 ka BP on the Middle Dnepr. The Middle/South Urals have a continuous record after 17 ka BP of small assemblages in caves and rock shelters and probably low population densities. These fluctuations in site numbers suggest major changes in mobility pattern and/or population size. Variation in site numbers, settlement patterns and population dynamics is accompanied by variation in cultural traditions (Table 2). In Western Europe, the cultural sequence shows considerable change and variation in the 24–17 ka period, with sites attributed to the Late Gravettian, Aurignacian V, Solutrean, and Badegoulian. The sequence in Eastern Europe shows a gradual change from Gravettian industries to Evolved Gravettian and finally Epigravettian industries. The Central European Early Gravettian gradually evolves into the Late Gravettian. The situation is unclear for the 20–17 ka period, when industries have been related to the French Badegoulian, survivals of Aurignacian traditions, developments within the local Gravettian and relations to the eastern Gravettian traditions (see Svoboda and Nova´k, 2004 for a review). One can only speculate at the moment to what extent population dynamics influence changes in technological traditions, the main component in defining archaeological cultures of the Upper Palaeolithic, but the population dynamics in southwestern France, if site numbers are used as proxy, may be associated with the cultural changes in the archaeological record.

Western Europe

Central Europe

17–12.4

Late Magdalenian Middle Magdalenian Early Magdalenian

Late Magdalenian

24–17

Badegoulian Solutrean Aurignacian V Late Gravettian

29–24

Gravettian (Perigordian)

Archaeology has paid most attention to processes of colonization. Housley et al. (1997) have discussed the chronology of the Late Magdalenian expansion based primarily on AMS 14C dates. They propose a two-phase process distinguishing a pioneer and a residential phase (cf. Davies, 2001). The discussion has focused on two aspects: the (statistical) analysis of the dates and the recognition of the initial, pioneer phase in the archaeological record (e.g. Blockley et al., 2000; Hazelwood and Steele, 2003). The record of short occupational episodes in Central Europe during the refuge period is of interest for the issue of initial colonization. Several small sites, north of the Alps, outside the abovementioned refuge areas, have been dated in the refuge phase. Several localities in Germany and Switzerland are dated to 20– 18 ka BP; some locations in Poland and the Czech Republic have dates around 15–14 ka BP. These sites are located at long distances from the contemporaneous main settlement areas. The locations can be interpreted as traces of far-flung hunting and collecting explorations, in the context of information gathering in marginal areas in times of relative resource abundance in the refuge areas (cf. Binford, 1983). As these explorations were not followed up by permanent residence in a region, the record of this short-lived initial phase is not overwritten by later occupation. A detailed study of these Central European sites during the refuge period can provide the outline of an archaeological signature for initial colonization to be confronted with the record of successful colonization in the Late Magdalenian and elsewhere. 6. Barriers to early modern human settlement 6.1. Faunal evidence from archaeological sites

Epigravettian

A pilot study of faunal data from archaeological sites in eastern Central Europe (Czech Republic, Austria, Slovakia, Poland and Hungary) was done to monitor changes in resource exploitation during the Pleniglacial, and the most preliminary of results are discussed here (Table 3). The mean number of herbivore species per site was calculated for different time windows. The mean number of herbivore species decreases from an initial number of 7 species per site to a final number of only 3 species per site. The main change occurs by 24 ka when the number drops from 7 to 4 species per site. The herbivore community is reduced to the core of reindeer and horse. Red deer becomes extinct and large herbivores such as mammoth, woolly rhinoceros and bison/aurochs are rare. The presence of saiga in the period 20–13 ka BP is significant. An even more prominent decrease in species diversity is visible among the carnivores. Large carnivores such as hyena and cave lion become virtually extinct. Wolf and fox remain as the most significant carnivores. The whole community structure is reorganized by the diminishing of species diversity. The initial ratio of about one herbivore species per carnivore species changes to three to four herbivore species per carnivore species. A first exploration of the importance of smaller mammals such as hares in eastern Central Europe suggests that their importance increases up to 25 ka, but is minimal in the period 24–13 ka BP. This

(Evolved)

Table 3 Summary of a pilot study on faunal data from eastern Central Europe.

Table 2 Main sequence of cultural traditions in the study area. Time window (ka)

5.3. Colonization processes and occupational episodes beyond the refuge areas

Eastern Europe

– hiatus –

Epi-gravettian /aurignacian Late Gravettian

Gravettian (Pavlovian)

Gravettian

Gravettian

Time window (ka)

N (sites)

Herbivora

Carnivora

Ratio (herbivora/carnivora)

17–13 24–17 29–24

6 6 5

2.5 3.8 7

0.7 1.8 5.8

3.6 2.1 1.2

Note: numbers refer to mean number of herbivore or carnivore species per site.

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may indicate that the decrease in herbivore diversity is accompanied by a decrease in smaller mammals and other alternative lowranking resources such as birds and may be carnivores (foxes and wolves). 6.2. Additional information Data from other parts of Europe provide additional information. Jochim (1987) describes changes in faunas from archaeological sites in southwest France. The number of big game species (more than just herbivores) found in archaeological levels is shown to decrease with the LGM and increase thereafter. The Gravettian levels (ca. 28–22 ka BP) contain 15 different big game species, whereas the subsequent Solutrean (22–19 ka BP) and Early Magdalenian (19–14 ka BP) contain 9 and 8 species, respectively. The Late Magdalenian levels (14–11 ka BP) contain 12 different big game species. Jochim (1987) also noted a significant difference in the initial situation between Southwest France and Southern Germany. The Gravettian in Southwest France contained 15 big game species, whereas the Gravettian in Southern Germany contained only 9 big game species. The number for Southern Germany is similar to the one for eastern Central Europe. Jochim indicates that the decrease in game species in absolute numbers is larger in France than in Germany, but the remaining number in France is sufficient to sustain a viable human population, whereas the number in Germany is too low and leads to local extinction. The same accounts for the situation in eastern Central Europe. Low resolution data for the number of carnivore species in northwestern versus southwestern Europe indicate similar patterns. Gamble (1984) notes that in the northwest the mean number of carnivores per site decreases from 4 for the EUP (35–20 ka) to 2 for the LUP (20–10 ka). In southwestern Europe this mean number remains about 1–1.5 for the entire period. Data for Eastern Europe do not indicate a major decrease in overall herbivore diversity. Changes occur mainly in range extension and possibly in population density. This pattern is supported by the floral evidence. A comparison of the Bryansk interstadial and the Last Glacial Maximum by Simakova (2001) indicates zonal changes in vegetations with an increase of steppe and periglacial forest-steppe vegetations on the loessic soils. But there are no substantial changes in the plant community structure. 6.3. Human ecology The relationship between settlement history and ecological variables is based on several assumptions. 1. Humans at the latitudes of Europe and under the climatic conditions of the last glacial rely heavily on animal resources

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for their energy supply, based on generalizations of ethnographic data. 2. Large herbivores such as reindeer and horse form the highest ranked game among the available resources, measured by the costs and benefits of hunting. 3. Long-term human occupation and survival of a viable population depends on the possibilities to buffer the risk of unpredictable fluctuations in crucial resources. Herbivore diversity can be taken as an approximation of the environmental constraints. A low diversity of herbivores combined with a high dependence on herbivores entails a high-risk environment. Under these circumstances, forager population levels are limited by prey availability (Boone, 2002). In times of failure due to unpredictable fluctuations in climate, herbivore population dynamics etc., no alternative food resources are available with extinction of a local population as a result.

6.4. Controls on herbivore diversity A model of global controls for modern herbivore diversity developed by Olff et al. (2002) offers the possibility of predicting patterning in herbivore diversity during the Pleniglacial. The model describes the relation of plants to herbivores in terms of plant abundance, plant quality and herbivore size. Plant abundance is high with high plant-available nutrients as well as moisture, but low when nutrient availability and/or moisture is low. Plant quality is low with low plant-available nutrients and high plant-available moisture, but high with high nutrients and low moisture. Any herbivore must encounter sufficient amounts of plant food and plant food of sufficient quality in order to persist. The limits of their persistence will be controlled by plant abundance and plant quality thresholds. Larger herbivores are more dependent on plant abundance, whereas smaller herbivores are more dependent on plant quality (Fig. 4). Olff et al. (2002: 902) note that larger herbivores are expected to be more abundant with greater moisture, relatively independent of plant-available nutrients. Smaller herbivores, in contrast, are expected to decrease with greater moisture and to increase with greater nutrient availability. The highest relative diversity of herbivores can be found in areas with moderate plant-available moisture and high plant-available nutrients, the lowest values in regions with both low moisture and low nutrient content. It should be noted that the model is based on a study of modern game parks, not taking into account the historical interactions between agriculture, herding and the development and policies of natural reserve parks. The model of global controls is in need of testing by paleontological information. Based on this model, the impact of the Last Glacial Maximum can be predicted. The main factor of climate change of immediate

Plant quality threshold

Grazer persists Plant abundance threshold Plant-available nutrients

Plant-available moisture

Plant-available moisture

Body mass small large

Plant-available nutrients

Fig. 4. Plant abundance and plant quality threshold control persistence of large and small herbivores (after Olff et al., 2002).

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relevance here is the change in aridity. As a consequence of lower moisture levels, plant abundance will fall. The impact on herbivore diversity will depend on the extent to which the levels fall below the critical thresholds for different size classes of herbivores. The impact of aridity in Europe will differ with the influence of the Atlantic Ocean. The boundary between the oceanic and continental influence will shift from east to west. Southwestern Europe will notice a decrease in moisture levels, but will not be as dry as Eastern Europe. It is expected that further to the east, the already arid conditions will increase relatively little. The impact of aridity is expected to be most severe in Northwestern and Central Europe. In the model, larger herbivores are more dependent on plant abundance than plant quality. With a decrease in plant abundance, larger herbivores will need to extend their range in order to get enough plant food. Therefore the available range is an important additional factor. The extension of the Alpine and especially the Fennoscandian ice sheet into the North European Plain limits the range available for foraging. Expectations are that the population of larger herbivores will diminish or go extinct in Central Europe due to the combination of low plant abundance and a small foraging area. The result will be a major decrease in herbivore diversity in Central Europe. A similar decrease in herbivore diversity is expected for Northwestern Europe. The model predicts an overall decrease of existing herbivore diversity. Diversity will decrease considerably in Southwestern Europe, but will not reach the low levels of Northwestern and Central Europe. The least change is expected in Eastern Europe. The model predicts a decrease of herbivore diversity in Northwestern and Central Europe, increased by the loss of foraging area due to the extension of the ice sheets. 7. Discussion The brief and preliminary survey of faunal data from archaeological sites supports the expectations based on the model of herbivore diversity. The model provides a reasonable explanation for changes in faunal composition, the virtual extinction of large herbivores such as mammoth, and the discontinuous settlement history of Pleniglacial Central Europe. A fauna containing only four herbivore species (mammoth, woolly rhino, horse and reindeer, see Table 4) in low population densities and without low-ranking backup resources seems to be an ecological community that is unable to sustain a viable population of early modern hunter–gatherers in Pleniglacial Europe. Several factors are important in the explanation of regional differences in settlement history. The initial situation of preexisting ecological diversity is the basis on which changes have their impact. Minor changes have a large impact in an area close to survival thresholds, whereas even major changes still have only limited impact in an area far above these thresholds. In addition, the local and regional geography is an important factor. If the biomass in this territory falls below a critical value, the species will have to relocate or become extinct. Finally, the settlement history suggests that aridity is a more critical factor than temperature. Settlement continued in Central Europe until the minimum temperatures were reached and only stopped afterwards in the most arid period of the Pleniglacial. Guthrie and Van Kolfschoten (2000: 17) have also argued for changes in herbivore behaviour. The climatic instability of the period selected for less territorial and more nomadic behaviour in larger herbivores such as horse and reindeer. Saiga antelope, entering Western and Central Europe around 20 ka BP, is known for this kind of behaviour nowadays and supports this argument. Though the model expectations are supported by the preliminary survey of archaeological faunas, these data are insufficient in several respects. The faunal data from archaeological sites give

Table 4 Main species of herbivore communities in Europe in the period 24–13 ka BP.

Mammuthus primigenius Coelodonta antiquitatis Bison priscus Ovibos moschatus Saiga tatarica Equus sp. Equus hydruntinus Cervus elaphus Rangifer tarandus Megaloceros giganteus Alces alces Capreolus capreolus Capra ibex Rupicapra rupicapra Sus scrofa

Southwest

Northwest

Eastern Central

Eastern

þ ? þ þ þ þ

þ þ

þ þ þ?

þ þ

þ? þ þ?

þ þ þ þ þ þ þ þ þ þ þ þ þ þ

þ

þ þ

þ þ?

þ þ þ ?

Note: ? Presence not certain; þ? Present but rare (Alces alces is probably present in the Hungarian Basin). Eastern Central: Eastern Central refers to the region north of and including the Hungarian Basin; fauna of the Southern Balkans includes Bovinae (Bos/Bison), Equus caballus, Cervidae (Alces/Megaloceros/Cervus), Capra ibex and Rupicapra rupicapra (Koz1owski et al., 1992). Eastern: diversity in the eastern province shows a gradient to increasing diversity in the southern latitudes and mountainous regions such as the Urals (Markova, 2003, pers. comm.).

a biased view because they document human subsistence strategies targeting the regional ecology. The fauna at the archaeological sites should be compared to faunal remains accumulated by other agents. In addition, herbivore diversity is a too restricted focus with regard to human subsistence. Alternative resources important for survival include small animals with high reproductive rates such as hares and rabbits, birds such as ptarmigan or seasonally migrating species, and even carnivores such as wolves and foxes. The availability of these animals should be taken into account. The model is also restricted by its focus on species diversity. The recolonization of the northern latitudes of Europe is accompanied by only small changes in species diversity. Changes in other alternative resources as mentioned above were important, but also the density of herbivore populations and the amplitude of annual fluctuations are crucial factors to consider. The LGM is probably characterized by a general decrease in productivity of the environment, but also by a major reorganization of the faunal communities with the virtual extinction of large carnivores. This ecological rearrangement is critical when comparing the abilities of Neanderthals and early modern humans in colonizing new environments. It seems that the last glacial maximum together with the quick warming at the Pleistocene/ Holocene boundary created a new environment that helped early modern humans to colonize the world. 8. Conclusion The settlement history of Pleniglacial Europe forms an interesting case study of early modern human hunter–gatherer adaptations. The abandonment of northern latitudes and the discontinuous settlement of Central Europe demonstrate some of the limits posed on modern human adaptations. These limits are ecological constraints on available animal resources. A herbivore diversity of four species, without the back-up of lower ranking resources, forms a barrier to long-term human settlement. No social process or technical aid is sufficient when environmental variables fall below critical thresholds for long-term human survival. Acknowledgements Research was conducted in the frame of Russian-Dutch Research Cooperation (NWO-RFBR project No. 047.019.007) as well as a post-

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