Abstract

Our knowledge of the evolution of human thought is limited not only by the nature of the evidence, but also by the values we bring to the authoritative scientific study of our ancestors. The tendency to see human thought as linear progress in rational capacities has been popular since the Enlightenment, and in the wake of Darwinism has been extended to other species as well. Human communication can be used to transmit useful information, but is rooted in symbolic processes that are nonrational—that is, they involve choosing among functionally equivalent alternatives, any of which is as good an option as any other. The evolution of human thought cannot be realistically isolated from the evolution of human society or human communication, neither of which is rooted in obvious rationality.