A short chronology for the peopling of the Tibetan Plateau

Archeological research over the past several years has started to provide evidence relevant to understanding both the timing of and processes responsible for human colonization of the Tibetan Plateau. This harsh, high-elevation environment is known to exact a heavy demographic toll on recent migrants, and such costs likely erected a substantial biogeographic barrier to initial human colonization. This chapter presents a series of simple metapopulation models that link processes of colonization to mutually exclusive archeological predictions. Current archeological evidence from the northern Tibetan Plateau suggests that seasonal forays into high elevation settings were "adaptive radiations" coincident with the appearance of both Early (ca. 30 ka) and Late Upper Paleolithic (ca. 15 ka) adaptations in low-elevation source areas around the Plateau. More permanent occupation of the Plateau probably did not begin before ca. 8200 ka and may have been driven by "competitive exclusion" of Late Upper Paleolithic foragers from low-elevation environments by emerging settled agricultural groups. The appearance of specialized epi-Paleolithic blade and bladelet technologies on the high Plateau, after 8200 ka, may indicate "directional selection" impacting 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 yr BP. The short chronology presented here contradicts genetic-based models suggesting that human populations may have been resident on the Tibetan Plateau for as long as 30,000 years. If the short chronology withstands further empirical scrutiny, it suggests either that initial colonists were genetically predisposed to the rapid accumulation of mutations leading to successful physiological adaptation, or that high-elevation selective pressures are much more severe than usually conceived.