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How climate disruptions revolutionized ancient human toolmaking

Impatient for your next smartphone upgrade? Just be glad you weren’t born hundreds of thousands of years ago, when the key technology for survival—stone hand axes—stayed almost exactly the same for 700,000 years. Researchers have long debated the reasons behind this long period of stasis. Now, a study of unusually detailed environmental data from an ancient lakebed in Kenya suggests a turbulent mix of climate change, tectonic activity, and rapid shifts in animal populations about 400,000 years ago forged new social and technological adaptations, including smaller obsidian blades and long-distance trade networks.

It’s an intriguing idea, says Nick Blegen, an archaeologist at the University of Cambridge who wasn’t involved in the study. But he cautions it’s impossible to draw broad conclusions about the motivations behind human technological advances from environmental conditions at a single site.

About 1.2 million years ago in Kenya’s Olorgesailie Basin, early members of our genus Homo began to make roughly hewn stone axes with flaked edges. These hand axes were a relatively sophisticated advancement over an even older, cruder stone tool technology. Ancient humans used their versatile, improved tools for a variety of tasks, including butchering animals, scraping hides, sawing wood, and digging up edible tubers. Their new stone technology, known as the Acheulean industry, persisted more or less unchanged for about 700,000 years.

Over that time, the toolmakers’ environment was remarkably stable, with abundant freshwater lakes and vast grasslands that nourished large animals like giraffes, buffalo, and elephants. But about half a million years ago, the picture gets murky, says Rick Potts, a paleoanthropologist at the Smithsonian Institution’s National Museum of Natural History, who led the new study. Large-scale erosion wiped out the archaeological record in the region from 500,000 to 320,000 years ago. By the time fossils and tools reappear at the end of this period, Potts says, it’s clear things had dramatically changed.

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