West African genomes show 2-19% ancestry from unknown extinct human species. Interbreeding occurred 43,000 years ago. Ghost population diverged 650,000 years ago from Homo sapiens lineage before Neanderthal split. Signal detected in Yoruba of Nigeria and Benin plus Mende of Sierra Leone. Non-Africans instead carry Neanderthal and Denisovan DNA. Ghost hominin lacks known fossils or location. Archaic DNA generally deleterious but some genes adaptive like Tibetan altitude gene from Denisovans. West Africans uniquely trace ancestry to this enigmatic ghost population. Study used genomic comparisons to Neanderthal and Denisovan references. Introgression best explains DNA segments in West Africans. Homo sapiens encountered multiple extinct species including this African ghost.