This thesis is a cross-disciplinary project, drawing on the techniques of behavioural ecology to reconstruct aspects of the socioecology of the early hominids. The modelling approach advocated in this project is an attempt to move towards the conceptual modelling approach forwarded by Tooby & DeVore (1986), moving away from referential and phylogenetic primate models to reconstruct hominid social behaviour. The project contributes to one current aim in palaeoanthropology; to develop a theoretical framework with which to reconstruct the behaviour of extinct taxa. The raw data for these models come from comparative analyses of behavioural ecology of extant primates. The fundamental basis of systems models of socioecology, is that the relationship between the environment and behaviour is characterised. The choice of environmental parameters has proved to be crucial, therefore I have characterised the key environmental variables that affect animals both directly (e.g. thermoregulatory stress), and indirectly (e.g. via habitat productivity). The quantitative relationships found in this chapter will serve as useful constants for further models. I first present a re-analysis of the systems models of baboons, refining previous models by R. Dunbar. The statistical techniques underlying these linear program models was further supported by the stability of the models when new data were included. Long-term climate data that were accurately sited were found to produce the most predictive equations. The results of the reanalysis of the baboon models gave support to their extension to another taxa. I then extend the range of the time-budget based models to the chimpanzees. The initial focus on chimpanzees is not solely because they are phylogenetic analogues. The emphasis of the models is that they are habitat specific. Relationships between behaviour and environment are used to develop functional equations to explore an animals flexibility of response to varying environmental conditions. Predictions could be made about: maximum ecologically tolerable group size, territory size, diet and extent of geographic range. The geographic distribution of chimpanzees predicted by the model was found to match very closely the current distribution. The models of chimpanzee, baboon and gelada socioecology were then compared. Dietary differences between the taxa accounted for their ecological niche separation. The models of extant primate systems models developed in this thesis provide a firm foundation for extending the models to extinct taxa. Preliminary models are presented, extending these analyses to the extinct australopithecines to forward the development of a conceptual model for the early hominids.