Is High Fidelity Imitation Necessary for Cumulative Culture? An Analysis of the Ratchet Argument

The so-called ratchet hypothesis, advanced in the 1990s by developmental and comparative psychologist Michael Tomasello, is the source of one of the most commonly reiterated platitudes surrounding evolutionary explanations of culture. The gradual, ever-increasing (and never decreasing) build-up of knowledge, skills, objects and innovations that accompanies our everyday existence is an unprecedented and unmatched human peculiarity—something that sets us apart from the rest of the biological world. This extraordinary form of culture, which is defined as cumulative, is attained by humans in virtue of our unique capacity to faithfully imitate each other. In this dissertation, I revisit the origins and development of this peculiar and extremely influential argument. I show how the original hypothesis by Tomasello has been progressively simplified and standardized to become an intuitive and extremely prolific (yet ironically not quite accurate) form of orthodoxy in cultural evolution studies and beyond. I then proceed to deconstruct this line of reasoning into its fundamental components: namely, imitation, high fidelity and cumulative culture. The conceptual and historical analysis of each term and of their theoretical connections will show that the simplicity and uniformity of the ratchet argument is only illusory. In reality, this argument allows for a bewildering variety of interpretations—resulting, in fact, in a multiplicity of slightly divergent “ratchet arguments”. My investigation will help to clarify why the argument elicits starkly opposed reactions, from enthusiastic endorsements to categorical dismissals. It may also assist in dispelling several (apparent) long term controversies. As for the reappraisal of the argument’s ultimate significance to evolutionary explanations of cumulative culture, I envisage a very narrow applicability. Of the many ratchet argument interpretations isolated in this work, only a minor proportion have something meaningful to say about the evolution of complex, cumulative cultural phenomena.