Weaning time in domestic sheep through carbon and nitrogen isotopes: Testing dentine sequential analyses in modern specimens

• Sequential δ 13 C and δ 15 N in dentine track weaning time in a modern sheep flock. • Artificial early weaning is detectable in dentine collagen. • First reference dataset for weaning time in domestic sheep provided. • The method enables studying sheep’s role in dairying in past economies. The age at weaning in domestic dairy animals is a focus of interest in archaeological research due to its connection to milk production. Artificial weaning (i.e., before natural weaning age) is a common strategy intended to balance physiological and nutritional needs of both mother and offspring while increasing milk supply for human consumption. Nitrogen stable isotope analyses of bone or dentine collagen have been widely used to reconstruct weaning histories in humans and other mammals, as they reflect the trophic step present in the dietary shift between breastfeeding and an exclusively solid diet. Specifically, sequential or intra-tooth δ 15 N analyses of dentine collagen allow exploration of this process with higher time resolution and the estimation of the age at which weaning occurs. While these approaches have been previously conducted on dairy cows, the topic has been barely explored in domestic caprines, partially due to the smaller tooth size and the lack of reference data for studying weaning time in these species. In this study, we implement sequential δ 13 C and δ 15 N analyses of dentine collagen in early-weaned (two months old) sheep from a modern experimental flock. We analyse the lower first molars of five specimens and assess the suitability of the approach for identifying artificial weaning in sheep dentine. The weaning process can be traced through the carbon and nitrogen isotope composition of dentine-collagen samples, and the position of dietary changes in the sequences is not affected by the dental developmental stage and the age of death. The study demonstrates that the method offers enough time resolution to track weaning practices in medium-size dairy species as caprines, and provides a first reference dataset for weaning time in domestic sheep. Implementing these incremental analyses in zooarchaeological assemblages would allow the investigation of human technical skills in managing lactation and weaning in the past, as well as the role of caprines in dairy production.