About 15,000 years ago, in the oldest known cemetery in the world, people buried their dead in sitting positions with beads and animal horns, deep in a cave in what is now Morocco. These people were also found with small, sophisticated stone arrowheads and points, and 20th century archaeologists assumed they were part of an advanced European culture that had migrated across the Mediterranean Sea to North Africa. But now, their ancient DNA -- the oldest ever obtained from Africans -- shows that these people had no European ancestry. Instead, they were related to both Middle Easterners and sub-Saharan Africans,...