Learning' is a process by which an individual gains new information. In the case of social learning’, this process occurs because at least one individual has undertaken an activity that results in another individual learning something new. For an individual, therefore,
learning' is an active process that takes place in vivo. For those faced with the challenge of studying learning in the Palaeolithic, however, all we are left with are inert objects (e.g., stone artefacts). Yet, understanding social learning during the Palaeolithic is a fundamental step toward understanding matters of our cultural evolution. Evolutionary biology, faced with similar problems, has made substantial progress in understanding matters of transmission, the effects of transmission on phenotypic variation, rates of mutation, etc. via the use of laboratory experiments, especially through the use of so-called model organisms’. Here, we describe two experiments that use handaxe form in the manner of a `model organism’ in order to understand the effects of copying error. We go on to discuss why understanding these micro-evolutionary effects can ultimately lead to a greater understanding of learning dynamics in handaxe-making hominin populations. These experiments illustrate that the characteristic size and shape parameters of handaxe traditions will have been inherently unstable. In the case of shape, in particular, this suggests that a learning mechanism other than pure observation of others’ artefacts was used. Individual (trial-and-error) learning could conceivably constrain variation somewhat, but costs associated with knapping would encourage the adoption of social learning mechanisms that would countermand the inevitable effects of copying error with reduced risk to tool manufacturers.