ABSTRACT
Reports of tool use by great apes are now routine, and include the use of sticks, sometimes trimmed and sharpened, for purposes as diverse as "termite fishing", probing for galagos in tree cavities, digging, pounding, defensive throwing, and depth-testing while wading. There is also evidence for tool cultures in that chimpanzee communities embody tool variations, and in some cases, diffusion between groups. Social learning also occurs, for example with capuchins acquiring nut-cracking behaviors by observing peers or older animals.
The encephalization quotient, a measure of brain size corrected for body size, is a surprisingly good initial predictor of tool use. Secondary factors include the evolution of specific brain mechanisms of praxis, and changes to the hands. However, precision grip is not exclusive to humans, even in pad-to-pad form.
The earliest hominin tools were sticks and other vegetation. Usage by nonhuman primates suggests we exploited such materials from the outset 7.5 million years ago, while the earliest known stone tools date from 3.3 million years ago. The large gap cannot be explained by the evolution of strong grip or hunting, as both predate stone tools.
Instead something cognitive must have occurred. Unsuccessful bonobo attempts to make stone tools suggest that it was our evolving ability to generate and sustain a mental model of a tool and how it is formed. Development of spatial ability and spatial memory may also have been needed.
The chapter discusses all of these issues. Tool types are covered from Lomewekian through Clovis cultures. Particularly important are hominin milestones in planning and understanding causality, supported by specific frontal and parietal brain mechanisms. Tool use in nonprimates is surveyed, as is the employment of tools and fire control in thermoregulation following our "Great Denudation".
