The fossil record for human evolution has provided a detailed picture for the course of brain enlargement from the c. 400cc brain size of early australopithecines at around 3.5 million years ago to the c. 1200–1500cc of modern humans. I discuss the relationship between this and the evolution of the human mind, arguing that neither brain size alone, nor arguments about changing networks within the brain, are sufficient to explain the patterns we can infer from the archaeological record about the development of human intelligence. The key event in the evolution of the modern mind appears to be when humans began to extend their minds by exploiting not just language, but also material culture and their social structures, as means of augmenting the mental capacities delivered by the brain alone.

Introduction

The last decade has seen a remarkable surge of interest in the evolution of the mind. This has arisen within a wide range of disciplines and been fostered by a considerable degree of inter-disciplinary cross-fertilisation at conferences and within edited publications (e.g. Barkow et al., 1992; Mellars and Gibson, 1996; Mithen, 1996b; Noble and Davidson, 1996; Bock and Cardew, 1997; Pinker, 1997b; Crawford and Krebs, 1998). Each discipline has, of course, a unique contribution to make to our understanding of cognitive evolution – psychologists bring to this topic a specialised understanding of modern minds, while neuroscientists, armed with their latest brain scanners, seek to extend our understanding of how the brain works. Archaeology has the benefit of being able to study the behaviour of human ancestors and relatives.