Peopling of the northern Tibetan Plateau

Early archaeological investigations on the Tibetan Plateau concluded that this harsh, high-elevation environment was successfully colonized around 30,000 years ago. Genetic studies have tended to support this view on the assumption that the uniquely evolved physiological capacities seen among modern Tibetan populations required long-term exposure to high-elevation selective pressures. Archaeological evidence amassed over the last decade suggests, however, that colonization leading to full-time occupation occurred much later. Seasonal foraging forays into high-elevation settings at c. 30 and 15 cal. ka appear to have been limited ‘adaptive radiations’ coincident, respectively, with the appearance of early and late Upper Palaeolithic adaptations in low-elevation source areas around the plateau. More permanent occupation of the plateau probably did not begin before c. 8200 cal. BP and may have been driven by ‘competitive exclusion’ of late Upper Palaeolithic foragers from low-elevation environments by emerging settled agricultural groups. The appearance of specialized epi-Palaeolithic blade and bladelet technologies on the high plateau, after 8200 cal. ka, may indicate ‘directional selection’ impacting on these new full-time residents. An ‘adaptive radiation’ of agriculturalists into the mid-elevations of the plateau, this time leading to year-round occupation, is again seen after 6000 cal. BP.