Western Caucasus regional hydroclimate controlled by cold-season temperature variability since the Last Glacial Maximum

The Caucasus region is key for understanding early human dispersal and evolution in Eurasia, and characterizing the environmental contrast between Last Glacial Maximum and Holocene is crucial for investigating human adaptation strategies to large climatic shifts. However, a paucity of high-resolution paleoclimate records leave this context largely unknown for early human populations in the Caucasus region. Based on our model-proxy comparison of high- and low-resolution records of 24 stalagmites from three caves, we find spatially distinct changes in vegetation and seasonality of precipitation, especially under glacial conditions. Supported by modern oxygen-isotope data and climate modeling, we identify a supraregional cold-season temperature control for oxygen isotopes in Black Sea speleothems, which previously had been interpreted as a local moisture-source signal. Carbon-isotope and trace-element data further suggest disproportionate changes in vegetation cover and soil dynamics at high altitudes, which would have resulted in a reduction but not a disappearance of human refugia during the Last Glacial Maximum, relative to the current interglacial. Our findings imply that abrupt climatic pressures from harsh conditions were overcome by adaptive strategies in the past.