There is no direct evidence for hunting predating Homo erectus, in either Homo habilis or in Australopithecus. The early hominid ancestors of humans were probably frugivores or omnivores, with a partially carnivore diet from scavenging rather than hunting. Evidence for australopithecine meat consumption was presented in the 1990s. It has nevertheless often been assumed that at least occasional hunting behavior may have been present well before the emergence of Homo. This can be argued on the basis of comparison with chimpanzees, the closest extant relatives of humans, who also engage in hunting, indicating that the behavioral trait may have been present in the Chimpanzee–human last common ancestor as early as 5 million years ago. The common chimpanzee (Pan troglodytes) regularly engages in troop predation behaviour where bands of beta males are led by an alpha male. Bonobos (Pan paniscus) have also been observed to occasionally engage in group hunting, although more rarely than Pan troglodytes, mainly subsisting on a frugivorous diet. Indirect evidence for Oldowan era hunting, by early Homo or late Australopithecus, has been presented in a 2009 study based on an Oldowan site in southwestern Kenya.