Coastal South Africa draws interdisciplinary interests due to the co-occurrence of a rich record for early human behavioral modernity, hyper-diverse vegetation with very high endemism (the Cape Floral Region), and globally influential oceanic and climate systems. High resolution and continuous climate and environmental records are needed to provide the context for the evolution of behavioral modernity and this diverse flora. Here we present the first such record for climate and environmental change from 90 000 to 53 000 years ago from the southern Cape coast. This important time span covers a burst of expression of several indicators of human behavioral modernity, as well as several key cycles in global climate change. Our research location is ideally placed near the location of several critical archaeological sites, near the boundary of the winter and summer rainfall regimes, and close to isotopically distinct floral zones. We used isotopic analysis of precisely dated speleothems to document shifting vegetation and rainfall, and show that the presence of winter rain and C3 grasses waxes and wanes in response to Southern Hemisphere shifts in SSTs and global temperature. When proxies of global temperatures indicate warmer conditions, δ18O and δ13C indicate more winter rain and more C3 grasses, respectively, and vice versa. This record displays abrupt and short-term changes previously undocumented. It is often argued that the Cape Floral Region partially owes its high diversity to relative climatic stability. Our record shows isotopic variability that at least matches that displayed in the Levantine Mediterranean system, so climatic stability may not have characterized the south coast. One short-lived phase of human technological innovation (the Still Bay) associated with early evidence for behavioral modernity occurs synchronous with an abrupt environmental perturbation. Early modern humans in this region confronted a variable climate and adapted quickly in a manner similar to behaviorally modern humans. © 2010 Elsevier Ltd. All rights reserved.