Our popular image of Homo erectus as the proto-guy who whose human-like traits all emerged at once needs overhauling, some anthropologists say. Sylvain Entressangle/Science Source hide caption

itoggle caption Sylvain Entressangle/Science Source

Language may have evolved in concert with tool making. Sergey Lavrentev/iStockphoto.com hide caption

itoggle caption Sergey Lavrentev/iStockphoto.com