阿尔泰山全新世适宜气候促进欧亚草原带史前人类扩张

How climate change in the middle to late Holocene has influenced the early human migrations in Central Asian Steppe remains poorly understood.To address this issue,we reconstructed a multiproxy-based Holocene climate history from the sediments of Kanas Lake and neighboring Tiewaike Lake in the southern Altai Mountains.The results show an exceptionally warm climate during～6.5-3.6 kyr is indicated by the silicon isotope composition of diatom silica(δ³⁰Sidiatom)and the biogenic silica(BSi)content.During 4.7-4.3 kyr,a peak in δ³⁰Sidiatom reflects enhanced lake thermal stratification and periodic nutrient limitation as indicated by concomitant decreasing BSi content.Our geochemical results indicate a significantly warm and wet climate in the Altai Mountain region during 6.5-3.6 kyr,corresponding to the Altai Holocene Climatic Optimum(AHCO),which is critical for promoting prehistoric human population expansion and intensified cultural exchanges across the Central Asian steppe during the Bronze Age.