Artifacts of the evolving mind: what tool use tells us about early human cognition

摘要

Modern human beings are unique both in their cognitive style and in their reliance upon complex technology to sustain their way of life; and there can be no doubt that it is our ability to reason symbolically that underwrites our familiar ability to dream up and (thanks to our dexterity) to make ever more complex tools. But it was not ever thus. Both our recent technologies and our symbolic consciousness clearly emerged from much simpler precursor states. The archaeological record begins with the appearance of the first simple stone tools some 2.5 million years ago, at a time when our hominid precursors still had essentially ape-sized brains and small, archaically-proportioned bodies. Between then and the end of the last Ice Age, some 12 000 years ago, Old Stone Age technologies became incrementally more complex (with vast spans of time typically elapsing between major innovations); and, slightly later, metabolically-expensive hominid brains began to expand (in a pattern poorly understood in detail, but that nonetheless shows a strong time-related trend towards greater size). Stone tools are, of course, the archaeologist's dream: they are the most durable of all products of human behavior, and have left an incomparable record. In frustratingly stark contrast, cognition is the most intangible of features and leaves no direct imprint: its qualities have to be guessed from physical proxies, among which brain size is sadly and notoriously imponderable.