An ecological and behavioural approach to hominin evolution during the Pliocene

• Carnivore turnover at approx. 3.5 Ma in East Africa coincides with radiation of australopiths.
• Parallel evolution of omnivory and sociality in carnivores and cercopithecines.
• The emergence of sociality in hominins may indicate that Australopithecus anamensis and Australopithecus afarensis differ at the species level.

The study considers the turnover in hominins, together with carnivorans and other primates, at 3.5 Ma against an environmental backdrop. Communalities are identified between evolving guilds that may directly inform hominin evolution. These are the evolution of (a) dietary generalists and (b) evidence for sociality in carnivores, baboons and hominins. Sociality and behavioural flexibility are regarded advantageous for the procurement of resources while, at the same time, reducing intraspecific competition; in primates it may initially also have served to reduce predation risk. Behavioural flexibility explains the evolutionary success of Panthera leo, Papio and Homo. Viewed within a wider palaeoecological and environmental context, it is possible that sociality in hominins, including allocare, were triggered by abiotic changes at about 3.5 Ma. If confirmed in future studies, this would mark the beginning of hominin life history evolution.