Teeth from a cremated child were excavated from a site believed to be 11,500 years old. The color differences show uneven burning. The scale is in millimeters. Science/AAAS hide caption

itoggle caption Science/AAAS

A new study finds that radio waves from a cell phone can affect the metabolism of brain cells, though there is no evidence that the effect is harmful. Here, a pedestrian talks on her phone on a street in San Francisco. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

Some 16,000 years ago, people may have been curling up next to the fire with red foxes. iStockphoto.com hide caption

itoggle caption iStockphoto.com