The Karku were an enigmatic race of the East and South native to Tanara, Vog Mur, and parts of the Mur Fostisyr. They were sometimes considered merely more intelligent Apes but usually seen as a race which was akin to both Trolls and Men, perhaps a kind of Half-Trolls or man- and troll-blooded Orcs. The Karku were divided into two sub-races, the more intelligent Krals and the rather primitive Garks
In other media
If adapted to a Middle-earth setting it would probably be most fitting if the Karku were considered creatures of Orc-kind, though they also could be a sub-group of man which had escaped Morgoth's experiments, similar to the Drúedain. Or they could be degenerate men, warped by the Shadow.