Researchers say they have discovered bits of foreign DNA in Africans that show a mysterious sister species may have lived on the earth with Neanderthals and humans.
"They had to be similar enough in appearance to anatomically modern humans that reproduction would happen," Joshua Akey of University of Washington in Seattle thinks. Human interbreeding is expected to have happened 20,000 to 50,000 years ago.
Researchers believe the mystery species lived only in Africa as the foreign DNA was not found in Europeans.
