Diversity of the relief and the Pleistocene environments of the mountain areas of SW Siberia played a major role in the history of the palaeolithic peopling of this territory. The geographical and contextual distribution of the cultural records reflects a climatic instability in the Altai area. Palaeoenvironmental proxy data indicate that the natural conditions during the earlier stages were generally more favourable for early human occupation than during the later stages. The cyclic nature of the glacial and interglacial periods led to periodic landscape transformations and generation of specific 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 the Middle Pleistocene interglacials accompanying the northern expansion of the temperate zone and biota. Mixed coniferous and broadleaf forests established in the tectonically active mountain zone with elevations of 1500-2000 m and parklands in the adjacent plains and continental basins provided a wide range of occupation habitats. There is limited evidence for persistence of Early Palaeolithic inhabitation during glacial stages due to inhospitable periglacial conditions. The last interglacial warming, indicated by re-colonization of southern Siberia by coniferous taiga forests, is linked with the appearance of the Mousterian tradition. Changes in the relief configuration influenced the local climate regime and opened new habitats for the Middle Palaeolithic population concentrated in the transitional zones of 500-1000 m elevation in the karstic area of the NW Altai foothills. Occupation of the central and southern Altai during the early last glacial was impeded by harsh, ice-marginal environments and expansion of glaciers in the valleys filled by large proglacial lakes. Progressive warming during the early mid-last glacial interstadial stage (59-35 ka BP) caused wasting of the ice fields accompanied by cataclysmic releases of ice-dammed lakes and large-scale erosional processes. Periodic outbursts of the glacial basins had a dramatic impact on the regional ecosystems, also obliterating the earlier cultural records. Appearance of the transitional early Late Palaeolithic stone industries reflects adaptation to mosaic interstadial habitats, including sub-alpine forest, 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 biological?) continuity in the broader Altai area during the Late Pleistocene. Re-establishment of cold tundra-steppe and tundra-forest habitats correlates with the Late Palaeolithic horizon with developed stone industries dominated by blade-flaking techniques. These techniques possibly survived in more protected locations characterized by warm microclimates in the northern Altai throughout the last glacial maximum (20-18 ka BP). Emergence of the microlithic assemblages with wedge-shape cores is linked with a new cultural adjustment in the final stage of the Palaeolithic development responding to transformations of the former periglacial ecosystems towards the end of the Pleistocene. (C) 2001 Published by Elsevier Science Ltd.
