Introduction and Overview

Abstract

In the 1960s Mary and Louis Leakey uncovered 1.8 million-year-old stone tools at the site of Olduvai Gorge in Tanzania. These tools, which archaeologists called the Oldowan industry, were later associated with 'Homo habilis', the first member of the genus 'Homo'. This was a significant discovery because relative to older hominin species that were not thought to be tool users, 'H. habilis' had a larger brain size and possessed anatomical features reminiscent of later species (e.g., reduced molar size, flatter face). Increasing cranial capacity, tool use, and more modern-looking features fit together in the story of what made humans unique. In fact, for the first time the use of material culture was included in the official definition of a species (Leakey, Tobias, and Napier 1964) - and thus the phrase "Man the Tool Maker" was coined (Oakley 1952). Since that time, our knowledge of the relationship between stone tools and the evolving human brain has grown and the resulting picture is predictably more complex. The earliest known stone tools now date to approximately 2.7 to 2.5 million years ago (mya) (Semaw 2000) whereas hominin evolution can be traced back using the fossil record to between 7.0 and 6.0 mya (see Wood 2002). Researchers question whether the "sudden" appearance of the Oldowan is the result of a dramatic change in cognitive abilities or the transition to a more archaeologically visible medium. One way to think about this is to consider the niche that was opened by the use of stone tools. Davidson and McGrew (2005; see also Davidson, Chapter 9) have suggested that the permanence of stone tools and the products of knapping on the landscape made a distinctive difference to the pattern of cognitive evolution. It also seems likely that 'H. habilis' was not the only stone tool maker and user. Depending on how many species one recognizes between 2.5 and 1.5 mya, up to as many as eight hominin species have been found in direct or indirect association with stone tools (Toth and Schick, 2005). In addition, there is now good evidence that early hominins were using bone tools (Backwell and d'Errico 2001, 2008).