Erectus Experiment: Fossil find expands Stone Age anatomy

During the heart of the Stone Age, from 1.7 million to 400,000 years ago, populations of our ancient ancestors in Africa, Asia, and Europe often served as brief evolutionary experiments, with most dying out before they established themselves as truly distinct species.

HEAD CASE. Two pieces of the 930,000-year-old African skull that has sparked debate over the nature of Stone Age evolution.