'Archaic introgressions' and 'ghost' DNA can reflect new paleohuman arrivals from Bioko
An exciting new paper by Fan, Tishkoff, and others on African population demographic history was published last week. The big mystery here is the 'ghosts', also called 'archaic introgressions.' There must have been an unidentified ('ghost') population of archaic humans living someplace, that contributed genes (introgression) to some of the known African populations. As you read this article, each time you read 'ghost' or 'archaic introgression' simply think 'paleohuman arriving from Bioko'.
Here are figures from this paper. Archaic introgressions are shown in grey text, grey dots, and grey boxes. My text additions are in pink. See the original figures here.