Pleistocene climate change, natural environments and palaeolithic occupation of the Altai area, west-central Siberia

Diversity of the relief and the Pleistocene environments of the mountain ar eas of SW Siberia played a major role in the history of the palaeolithic pe opling of this territory. The geographical and contextual distribution of t he cultural records reflects a climatic instability in the Altai area. Pala eoenvironmental proxy data indicate that the natural conditions during the earlier stages were generally more favourable for early human occupation th an during the later stages. The cyclic nature of the glacial and interglaci al periods led to periodic landscape transformations and generation of spec ific ecosystems adjusted to particular topographic settings and responding to climatic variations. The initial occupation of the broader Altai region associated with "pebble- tool" industries from alluvial formations likely occurred during some of th e Middle Pleistocene interglacials accompanying the northern expansion of t he temperate zone and biota. Mixed coniferous and broadleaf forests establi shed in the tectonically active mountain zone with elevations of 1500-2000 m and parklands in the adjacent plains and continental basins provided a wi de range of occupation habitats. There is limited evidence for persistence of Early Palaeolithic inhabitation during glacial stages due to inhospitabl e periglacial conditions. The last interglacial warming, indicated by re-colonization of southern Sib eria by coniferous taiga forests, is linked with the appearance of the Mous terian tradition. Changes in the relief configuration influenced the local climate regime and opened new habitats for the Middle Palaeolithic populati on concentrated in the transitional zones of 500-1000 m elevation in the ka rstic area of the NW Altai foothills. Occupation of the central and souther n Altai during the early last glacial was impeded by harsh, ice-marginal en vironments and expansion of glaciers in the valleys filled by large proglac ial lakes. Progressive warming during the early mid-last glacial interstadi al stage (59-35 ka BP) caused wasting of the ice fields accompanied by cata clysmic releases of ice-dammed lakes and large-scale erosional processes. P eriodic outbursts of the glacial basins had a dramatic impact on the region al ecosystems, also obliterating the earlier cultural records. Appearance of the transitional early Late Palaeolithic stone industries ref lects adaptation to mosaic interstadial habitats, including sub-alpine fore st, dark coniferous forest, mixed parklands and open steppe. The identical geographical distribution of the Middle and Late Palaeolithic sites and the time-transgressive lithic technologies suggest a regional cultural (and bi ological?) continuity in the broader Altai area during the Late Pleistocene . Re-establishment of cold tundra-steppe and tundra-forest habitats correla tes with the Late Palaeolithic horizon with developed stone industries domi nated by blade-flaking techniques. These techniques possibly survived in mo re protected locations characterized by warm microclimates in the northern Altai throughout the last glacial maximum (20-18 ka BP). Emergence of the m icrolithic assemblages with wedge-shape cores is linked with a new cultural adjustment in the final stage of the Palaeolithic development responding t o transformations of the former periglacial ecosystems towards the end of t he Pleistocene. (C) 2001 Published by Elsevier Science Ltd.