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Capturing climate variability during our ancestors' earliest days

Climate’s role in shaping the environmental and evolutionary history of our earliest ancestors remains an actively debated topic. In PNAS, Magill et al. (1, 2) present records of terrestrial habitat and hydroclimate variation and pacing from Olduvai Gorge sediments during a key interval of our ancestors' divergence and dispersal approximately 2.0 Ma. Although there is general consensus that ecosystem variability shaped resource and landscape distributions on the East African landscape, causing changes in early Homo foraging strategies and diet (3⇓–5), the temporal linkages between climate and environmental changes and hominin evolution remain far more contentious (6). Here, Magill et al. constrain some of these temporal linkages by extracting paleoclimate records of terrestrial plant community change and hydrological cycle dynamics from well-dated, continuously deposited lake sediments associated with hominin archaeological sites. These new archives of terrestrial ecosystem variability reveal distinct orbital pacing in precipitation that drove abrupt changes in the local plant community and shaped the landscape’s water availability during an important interval of hominin evolution.