Early Hominin Stone Tools
The simple fact of tool-making no longer provides a sharp dividing line between “Man the Tool-Maker” and the rest of the animal world. It is now clear that many other species make and use tools, and that distinctly human technology emerged through a long and meandering evolutionary process rather than the crossing of some critical threshold. However, it would be a mistake to underestimate the transformative effects of tools on everything from our hands and brains to our reproductive strategies and social organization. Humans may not be uniquely defined as “a tool-using animal” but we do inhabit a uniquely elaborated technological niche. The earliest known stone tools predate evidence of brain expansion by many hundreds of thousands of years during which their occurrence was extremely patchy and discontinuous. Far from a breakthrough, stone tool-making appears to have been a fragile behavior of marginal value. This is expected for a technology located near the limits of contemporary hominin capacities, with high learning costs, limited flexibility, and high rates of failure offsetting it benefits. Natural selection acting on hominin brains and bodies during this lengthy period of experimentation may eventually have eased these costs, leading to a dramatic proliferation of “Oldowan” tool-sites after about 2.0 million years ago (mya). This is closely co-incident with the first appearance of larger-brained and –bodied Homo erectus by ~1.9 mya and was rapidly followed by the invention of more sophisticated Acheulean “handaxe” technology by 1.76 mya, marking an important inflection point in the biocultural feedback processes that eventually produced the modern human technological niche.