Dramatic shifts in the East African climate may have driven toolmaking advances and the development of trading networks among Homo sapiens or their close relatives by the Middle Stone Age, roughly 320,000 years ago. That’s the implication of discoveries reported in three papers published online March 15 in Science.

Newly excavated Middle Stone Age tools and red pigment chunks from southern Kenya’s Olorgesailie Basin appear to have been part of a long trend of climate-driven behavior changes in members of the Homo genus that amped up in H. sapiens. Locations of food sources can vary unpredictably on changing landscapes. H. sapiens and their precursors responded by foraging over larger areas with increasingly smaller tools, the researchers propose. Obsidian used for the Middle Stone Age tools came from far away, raising the likelihood of long-distance contacts and trading among hominid populations near humankind’s root.

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