http://www.sciencemag.org/news/2020/10/how-climate-disruptions-revolutionized-ancient-human-toolmaking

Workers from a Nairobi, Kenya, drilling team mark sections of a sedimentary core drilled from Kenya’s Koora Basin.

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.