Identifying social learning between Roman amphorae workshops through morphometric similarity

Abstract

The aim of this study is to identify dynamics of social learning between amphorae workshops during the the Roman Empire. The Baetica province developed a massive infrastructure of olive oil production that supplied the Western provinces of Rome for almost 300 years. The olive oil produced in this area was shipped through maritime and riverine transport networks in a standardized amphoric shape made in several workshops spread around the region. These workshops have generated a large amount of evidence but it is still difficult to understand through archaeological proxies how the production of amphorae was organized. We apply here an evolutionary framework to find links between workshops through the morphometric similarities of the amphorae they produced. The suggested approach identifies how individual potters acquired and transmitted technical skills by exploring small yet statistical significant differences in the amphorae made in 5 different workshops. Multivariate methods are used to cluster a variety of amphorae based on morphometric measurements and the outcome shows that the analysis is useful even when a high degree of standardization exists, such as was the case for Roman amphorae (i.e. Dressel 20). Results suggest that morphometric similarity is inversely correlated with spatial distance between workshops. This pattern suggests that pottery-making techniques were transmitted through oblique transmission with little or no movement of potters between distant workshops. The conclusion is that morphometric similarity may be an effective proxy to identify social learning dynamics even amongst workshops producing exactly the same amphoric type.