Sivapithecus is east and Dryopithecus is west, and never the twain shall meet

Sivapithecus and Dryopithecus are well-described Miocene hominids (great apes and humans), both known since the 19th century. Over the years these genera have been combined into one (Dryopithecus) or separated up to the subfamily level. Each have been dismissed as interesting side branches, hailed as direct ancestors, or recognized as sister clades to one or more clade of extant hominid. Here I argue that they are each stem taxa of the two living hominid clades Ponginae and Homininae. A famous poem by Rudyard Kipling tells the tale of a British and Afghan soldier whose differences (in ethnicity) obscure their similarities (in character). The relationship between Sivapithecus and Dryopithecus is similar. On the one hand, Sivapithecus is restricted to South Asia, has thickly enameled molars, robust jaws, and superficially baboon-like forelimbs; Dryopithecus is European, has thinly enameled molars and gracile jaws, with suspensory forelimbs. On the other hand, both are great apes, both had suspensory adaptations, large brains, and delayed development, and both are closely related to living hominids. Recognition of the likely relations of Sivapithecus and Dryopithecus provides insight into the causes, timing, and paleobiogeography of crown hominid origins.