A revised edition of an obscure 1960 paperback: another excellent anthropological sf novel, with less padding and more substance than the better-known The Shores of Another Sea (1983). The human-alien Merdosi of Sirius walk upright like humans, but also have long powerful arms and can brachiate through the trees like apes. They have a sophisticated language, but apparently no culture or technology at all (not even clothing or fire)--but they do seem to control various animal species, including a hunting-dog creature. Anthropologist Monte Stewart's study team lands carelessly, confident that the Merdosi are primitives--but the team is soon destroyed in a vicious attack led by the natives' dog-creatures. Though his wife is one of the victims, Stewart looks past his grief and anger to realize that the Merdosi culture depends upon biological manipulation and mental gifts; so he will stake his life on a last attempt to communicate with, and comprehend, the Merdosi before the Earth military occupy the planet, ending all hope of friendly contact. Structurally much more convincing than Shores, with sound anthropological and alien-contact ideas worked into a fascinating plot: a genuine neglected classic.