Statistically robust representation and comparison of mortality profiles in archaeozoology
Résumé
Archaeozoological mortality profiles have been used to infer site-specific subsistence strategies. There is
however no common agreement on the best way to present these profiles and confidence intervals
around age class proportions. In order to deal with these issues, we propose the use of the Dirichlet
distribution and present a new approach to perform age-at-death multivariate graphical comparisons.
We demonstrate the efficiency of this approach using domestic sheep/goat dental remains from 10
Cardial sites (Early Neolithic) located in South France and the Iberian Peninsula. We show that the
Dirichlet distribution in age-at-death analysis can be used: (i) to generate Bayesian credible intervals
around each age class of a mortality profile, even when not all age classes are observed; and (ii) to create
95% kernel density contours around each age-at-death frequency distribution when multiple sites are
compared using correspondence analysis. The statistical procedure we present is applicable to the
analysis of any categorical count data and particularly well-suited to archaeological data (e.g. potsherds,
arrow heads) where sample sizes are typically small.