Humanity has an intimate relationship with the Earth’s climate system: we drive climate changes, and conversely, must respond and adapt to shifts in the climate. Our ancestors likely experienced similar interactions, but our knowledge of how, or whether, early humans migrated or shifted their settlement patterns in response to climatic shifts is hindered by limitations of both the archaeological and paleoclimate record. In this talk, I will present ways in which we have addressed this issue using biomarker-based reconstructions of aridity in both west and east Africa. We have found compelling evidence that major shifts in early human behavior corresponded with humid/arid transitions, highlighting the role of rapid climate change in driving migration and lifestyle shifts.