National Geographic: Sex in the Stone Age 2012

A fragment of a pinky bone and a tooth twice the size of today's average molar are the only remnants of a species we now know lived at the same time and place as modern humans—and interbred with them. They are a part of us we never knew existed. What did these "people" look like? And how do they fit into what we thought we knew about our biological development as a species?