WASHINGTON, D.C.—According to a Science News report, Rick Potts of the Smithsonian Institution and his colleagues suggest that early humans may have entered the Middle Stone Age tens of thousands of years earlier than previously thought. The researchers analyzed soil samples taken from the Olorgesailie Basin of Kenya’s Rift Valley, and noted that frequent changes in the climate and earthquakes transformed the resources available to human ancestors. Erosion has destroyed about 180,000 years of the geological record at the site, but Potts said that during that time, there must have been a rapid period of evolution because lumps of pigment and new types of tools appear when the geological record resumed some 320,000 years ago. The toolmakers had shifted from sharpening large hand axes to making smaller tools, such as sharp flakes mounted on spears to be used as projectiles, and blades and points made from obsidian. Obsidian is not available locally, which suggests the toolmakers had to travel and perhaps interact with other human groups to obtain it. No hominid fossils have been found at the site, however, so researchers cannot be sure that Homo sapiens made the artifacts. For more, go to “The First Toolkit.”