Probably "Sands of the Kalahari" (1965).
Andrew's 100% correct, it is Cy Endfield's "Sands of The Kalahari" and the actor concerned is Stuart Whitman.
www.imdb.com/title/tt0059675SPOILERThe ending is left purposely ambigious: Stanley Baker and Susannah York are rescued and Stuart Whitman remains behind in the desert, either becoming baboon chow or becoming the king of the desert baboons.