A unique characteristic of our species is that recent evolution has proceeded in two dimensions: biological and cultural. From a paleoanthropological perspective, the past two million years are defined as much in terms of cultural innovations as they are in terms of morphological change. The recognition that humans have been shaped by the intersection of two evolutionary processes has led to much speculation about the degree of interdependence and interaction between cultural and biological evolution. Attempts to understand the interplay between the two processes have ranged from metaphysical speculations (Teilhard de Chardin, 1957) to specific mathematical models (e.g. Cavalli-Sforza & Feldman, 1981; Lumsden & Wilson, 1983). However, apart from some broad generalizations, the parameters of this interaction remain undefined. In particular, we have little concrete knowledge about whether the tempo and mode of evolutionary change are concordant from one realm of evolution to the other. In part, this is because there are no wholly satisfactory measures of the cultural components of evolution: the cultural attributes that have been examined are either too superficial and ephemeral (e.g. incised patterns on pottery), or so fundamental to human behaviour that the interplay between biology and culture is inextricably intertwined (e.g. the transition between Oldowan and Acheulian).