Modern humans, or homo sapiens, are the only living species in their genus, but history teaches us that several other species of ancient humans have existed. Take the Denisovans, whose remains were found in a Siberian cave in 2008. Geneticists sequenced their genome and it was revealed they evolved from an unknown species with dark skin, brown eyes and brown hair, unlike their Neanderthal cousins. They are believed to have gone completely extinct. Hear about nine other mysterious extinct human species in this edition of Hybrid Librarian.