Trio of studies track stone tool technology in Kenya

by Mary Caperton Morton
Tuesday, June 5, 2018

About 300,000 years ago, East Africa was a hotbed of human evolution and innovation. Sweeping ecological changes contributed to the emergence of modern humans, and spurred the first long-distance trade routes and novel toolmaking technologies. Three new studies published in Science shine a spotlight on Kenya’s Olorgesailie Basin, where the clunkier Acheulean tool technology gave way to the smaller, sleeker Middle Stone Age tool technology famously associated with Homo sapiens.

In the first study, Rick Potts, an anthropologist at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., and colleagues analyzed artifacts and well-preserved sediments from Olorgesailie Basin to track ecological changes across the floodplains-turned-grasslands over a period of 1.2 million years. They found that grasslands spread across the region starting roughly 800,000 years ago, attracting smaller species of grazing animals that would have provided new hunting opportunities for early humans.

A second study, led by Alison Brooks, also of the Smithsonian Institution, cataloged stone tool artifacts found in the Olorgesailie Basin that are between 500,000 and 298,000 years old. They found that the older tools were bulkier and made from local volcanic rock, whereas the later tools were more refined and more often crafted from obsidian or chert from sources up to 90 kilometers away, suggesting trade routes had begun to spread across the landscape.

In the third study, detailed dating of the sites and artifacts was provided by geochronologist Alan Deino of the Berkeley Geochronology Center in California and colleagues. Using argon and uranium isotopic dating, Deino’s team developed a timeline for the sites scattered throughout the Olorgesailie Basin. The study helped pinpoint the transition from the older Acheulean tools to the first Middle Stone Age tools at about 320,000 years ago, making the Middle Stone Age artifacts identified in the new studies the oldest examples found to date in eastern Africa.

Taken together, the trio of studies paints a picture of climate-driven innovation at one of the most pivotal times in human evolution, Potts and colleagues wrote in Science.

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