The southern African cercopithecid (monkey) fauna has undergone a profound change in composition and diversity since the Plio-Pleistocene, with modern species representing only a small part of the diversity that existed in the past. During the Plio-Pleistocene, eleven cercopithecid species were found in southern Africa, as many as six of which might have been contemporaneous. The move to more open environments, plus dispersal from and to southern Africa, have probably contributed significantly to changes in monkey diversity over the past three million years. Some of the Plio-Pleistocene cercopithecids are likely to have lived in the same ecological communities as hominins. In modern primate communities, niche partitioning is sometimes used as a way to minimise competition for resources. This would have been a plausible way to maintain relatively high species diversity in the Plio-Pleistocene primate fauna of southern Africa. Nonetheless, the presence of hominins in the generalist feeder niche could have affected the behaviour of other primates in their communities, specifically the monkeys that today have an eclectic diet. It is also possible that Plio-Pleistocene hominins influenced community structure and behaviour through predation. In conclusion, environmental changes as well as interaction with hominins each contributed to shaping the community structure that is seen in South African monkeys today, but further work is required to reconstruct in more depth the interactions of the ecological communities to which hominins belonged.