Ann Gibbons | Science
More than 320,000 years ago in the Rift Valley of Africa, some early innovators adopted a new technology: They eschewed the clunky, palm-size stone hand axes that their ancestors had used for more than a million years in favor of a sleek new toolkit. Like new generations of cellphones today, their Middle Stone Age (MSA) blades and points were smaller and more precise than the old so-called Acheulean hand axes and scrapers.
These toolmakers in the Olorgesailie Basin in Kenya chose as raw materials shiny black obsidian and white and green chert, rocks they had to get from distant sources or through trade networks. In another first, they chiseled red and black rocks, probably to use as crayons to color their bodies or spears—an early sign of symbolic behavior.
“This is indicative of a gear change in behavior, toolmaking, and material culture,” says evolutionary psychologist Robin Dunbar at the University of Oxford in the United Kingdom, who studies social networks.
