The spatial distribution of Neanderthals was strongly influenced by the climatic fluctuations of the late Middle and early Upper Pleistocene. Middle Paleolithic sites and Neanderthal fossils have been discovered across much of western Eurasia, below 55°N latitude. However, this vast geographical area has been unevenly and discontinuously populated over the course of time. Vast areas remained unoccupied during the coldest phases. On a smaller geographic scale, there were also variations in the density of sites, reflecting both the more or less favorable conditions for their preservation and the availability of resources at the time they were inhabited.
Neanderthal populations adapted to a variety of environments. They exploited both the forested landscapes of interglacial periods and the much more open landscapes of glacial periods. However, they hardly prospered in peri-arctic environments. In the Alps and Jura, Mousterian sites discovered at altitudes of up to 2,000 m were occupied during the mildest periods, and probably on a seasonal basis. In some peripheral regions (British Isles, Central Asia), the Neanderthal presence was intermittent, depending on climatic conditions and their effects on geography. In the Levant, Neanderthal populations and modern humans of African origin alternated during the Middle Paleolithic. Group movements can be reconstructed by analyzing the raw materials used to make lithic tools, and individual movements by analyzing strontium isotopes in tooth enamel.
