Two species, two stories: divergent morphometric evolution of sheep and goats over the last 8000 years

Since their domestication about 10 500 years ago, sheep and goats have been central to human subsistence economies. Despite shared traits and frequent co-herding, these species are biologically distinct, with their uses reflecting diverse cultural practices. Advances in geometric morphometrics enable detailed analyses of their phenotypic evolution, shaped by natural and artificial selection, genetic drift and gene flow. These evolutionary mechanisms are often challenging to disentangle in archaeozoology, but patterns of morphometric variation can reveal evolutionary parallels and divergences. This study investigates the morphometric evolution of sheep and goat teeth in the northwestern Mediterranean basin over 8000 years. Dental remains, which preserve well in archaeological contexts, provide rich data for evolutionary studies, including species-level identifications. Using two-dimensional geometric morphometrics, third lower molars from 1602 sheep and 635 goats, spanning archaeological and modern specimens, were analysed. Molar size, shape and variance were compared across six chrono-cultural phases, tracing diachronic morphological changes. Distinct patterns emerge: sheep exhibit greater variability likely reflecting selective breeding for diverse purposes. Goats, in contrast, show greater uniformity. These findings underscore unique evolutionary trajectories for sheep and goats, offering new perspectives on their biocultural evolution within the dynamic environmental and anthropic contexts that shaped their current diversity.This article is part of the theme issue 'Unravelling domestication: multi-disciplinary perspectives on human and non-human relationships in the past, present and future'.