Toward a “quantitative genetic” approach to lithic variation

Lithic artifacts are increasingly being used to address questions in evolutionary, i.e., historical, terms. The explicit assumption in such analyses is that lithic attributes reflect patterns of inheritance via social learning. However, both raw material and reduction factors are known to be potential sources of lithic variation. The cultural-evolutionary analysis of lithic variability must, therefore, reconcile heritable and nonheritable sources of variation under a single coherent framework. Moreover, there is a frequent assumption that conveniently measureable features, such as the relative shape of a biface at a specific point of its length, can be used as indicators of heritable variation. The use of such traits, however, is potentially questionable, especially in the light of controlled experiments that indicate that traits such as platform depths and angles influence the form of individual flakes. As such, it may be reasonable to consider whether such features represent more appropriate analytical units. Here, we contend that the solution to these problems lies in application of a “quantitative genetics” approach, which was designed to solve directly analogous problems in biology. This approach explicitly models multiple sources of variation simultaneously. Moreover, it provides a logical rationale for how evolutionary forces (e.g., drift and selection) can operate when only part of this variation is potentially heritable. We outline specifically how quantitative genetic theory can be rewritten for use with lithic artifacts. Thereafter, we provide example analyses of data, which support our case. We conclude by summarizing the merits of this framework and outline future extensions.