for the appearance of modern human characteristics-- movement to the savanna, bipedalism, tool use, hunting, brain enlargement, etc. (e.g., Campbell 1966) To Isaac, these "simple additive models" were untenable since some of the behavior to be accounted for was already present if only in primitive form in the repertoire of wild chimpanzees. As early as 1971, he argued in favor of integrated models.
             "Integrated growth is a better analogue than chain reaction. Thus I would favor models involving concurrent development with mutual reinforcement of adaptive advantages by matching changes in all components, and from this stance I would argue that hunting, food sharing, division of labor, pair bonding, and operation from a home base or camp, form a functional complex, the components of which are more likely to have developed in concert than in succession. It is easy to see that tools, language, and social cooperation would fit into the functional complex as well, and very likely had equally long development histories within the overall system." (Isaac 1972)
             Isaac's intuition was probably reinforced by his Ph. D. research at Olorgesaile, a Homo erectus site in Kenya. Olorgesaile, dated to between 900,000 and 400,000 years ago, almost certainly did function as a home base (Potts 1988:292). Moreover, it was discovered and first excavated by Louis and Mary Leakey, who saw evidence of home bases ("living floors") at a number of hominid-formed sites in East Africa, including some in Olduvai Gorge. No doubt this common-sense interpretation, which in some respects goes back as far as 1933 to Solly Zuckerman (Potts 1988:251), had rubbed off on Isaac, but he had also become convinced that lower Paleolithic artifact assemblages were peculiarly difficult to interpret because of low sample densities which produced erratic and potentially misleading data. Discussing this in his 1972 paper, he went on to suggest that paleoarchaeologists were be...