Farming helped fuel the rise of civilizations, but it may also have given us less robust bones. Leemage/UIG via Getty Images hide caption

itoggle caption Leemage/UIG via Getty Images

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

A mother and daughter herd their yaks along a highway on the Tibetan plateau. Frederic J. Brown/AFP/Getty Images hide caption

itoggle caption Frederic J. Brown/AFP/Getty Images

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

itoggle caption Sergey Lavrentev/iStockphoto.com

Bonobos share a piece of fruit at the Lola ya Bonobo sanctuary in the Democratic Republic of Congo. Jingzhi Tan/Duke University hide caption

itoggle caption Jingzhi Tan/Duke University