This 2013 photo provided by ASU graduate student Chalachew Seyoum shows him holding a 2.8 million years old jawbone fragment he found at an archaeological dig in Ethiopia. The site is not far from where Lucy was unearthed. Africa is a hotbed for human ancestor fossils, and scientists from Arizona State University have worked for years at the site in northeast Ethiopia, trying to find fossils from the dimly understood period when the Homo genus, or class, arose. (AP Photo/Chalachew Seyoum)