Each human gene is present once in the Neanderthal genome. Neanderthals were humans, more than 99.9% identical in DNA to modern humans. Svante Paabo has a book out now, that tells all about the sequencing of the Neanderthal and Denisova genomes, and what they found in them: http://www.amazon.com/Neanderthal-Man-Search-Lost-Genomes/dp/0465020836