Hominin Stone Flaking and the Emergence of ‘Top-down’ Design in Human Evolution

Abstract

The philosopher Daniel Dennett argues that complex structures in the natural and cultural worlds emerge from two types of design. Bottom-up design involves the rote action of a simple algorithm in an environment constrained by physical laws. Top-down design involves deliberation and planning, and is unique to modern humans. Identifying the emergence of top-down design in the hominin lineage is an important research challenge, and the archaeological record of stone technology is our best evidence for it. A current view is that artefact types and flaking methods increased in complexity from 3.3 toc.0.3 million years ago, reflecting improving capacities at spatial cognition and working memory, culminating in top-down design perhaps as early as 1.75 million years ago. Recent experimental work, however, has shown that a simple ‘remove flake’ algorithm constrained by the laws of fracture mechanics—a form of bottom-up design—can produce stone tool attributes thought to be evidence of top-down design. Here, these models are reviewed and critiqued in light of the new experimental evidence. A revised working memory-based model, focusing on the recursive aspects of stone flaking, is proposed.