Precipitation dynamics in southern central Asia during marine isotope stage 5: Implications for early modern human dispersal

Past warm periods provide important analogues for future warming. Marine Isotope Stage 5 (MIS 5, ∼130–∼70 ka) – the most recent warm interglacial – serves as a crucial testbed for evaluating potential impacts of future climate change on Central Asian hydroclimate, yet high-resolution precipitation records from this vast region remain exceptionally sparse. Consequently, the mechanisms governing MIS 5 moisture variability across Central Asia (CA), and their broader implications for ecosystem dynamics and early human dispersals, are still poorly resolved. This study reconstructed precipitation variability in Tajikistan, southern CA, during MIS 5, using principal component analysis of multiple paleoclimatic proxies preserved within loess deposits. The results reveal that the precipitation pattern in southern CA differs markedly from those in other parts of Eurasia. We investigated the likely factors influencing the difference using Convergent Cross-Mapping (CCM), and identified a fundamental transition around 102 ka for precipitation dynamics in southern CA, moving from a predominantly westerlies-forced state to a regime limited by moisture availability in source regions. Temperature-driven atmospheric moisture emerged as the primary determinant. Our findings offer valuable insights into near-future climate scenarios in southern CA, such as a likely regional increase in rainfall. Based on the MIS 5 precipitation reconstruction, we argue that the dominance of cold-season precipitation in southern CA may have impeded the northward migration of anatomically modern human (AMH) during MIS 5 north of the Central Asian mountains. We therefore recommend incorporating precipitation seasonality into simulations of AMH dispersal as a factor influencing dispersal routes and timing.