Child-mother relationships and childhood dietary patterns in the Iberian Peninsula uncovered by Bayesian isotopic approaches

This study examines trends in infant diet, breastfeeding and weaning in Portugal through time in Roman, Medieval Muslim and Christian skeletal assemblages (1st to the 15th century CE). New stable carbon (δ13C) and nitrogen (δ15N) measurements were collected from 143 non-adults and 46 adults that are analysed alongside comparative published datasets from contemporaneous Iberian populations. A statistical package was used to model bone collagen nitrogen isotope data of individuals, quantitatively estimating weaning onset and completion across diverse historical sites. Nutritional intake from infancy to adolescence was reconstructed via Bayesian modelling supported by the OsteoBioR platform using incremental dentine-collagen isotope ratio analysis in six adult individuals. Childhood diets in historical Portugal showed a prolonged weaning time while weaning food included varying degrees of high trophic level protein during both the Roman and Medieval periods. The Bayesian statistical approach offers a comprehensive perspective on child-rearing practices through the lens of diet, including breastfeeding, weaning and nutritional intake during childhood in historical Portugal. The results highlight the variability and complexity of childhood diets over time and between different locations. Overall, the study informs debates about child nutrition practices globally while also offering unique insights into infant nutrition in Iberia over nearly 1500 years.