© 2021 The AuthorsTraditional methods for estimating age-at-death of caprines are based on dental and epiphyseal fusion data and known to produce rather wide age intervals. In order to better interpret prenatal to early infantile mortality of sheep in prehistoric assemblages more precise age predictions are needed. We address this issue using a Generalized Additive Model (GAM) developed on humerus measurements of unborn and very young sheep of known age housed in modern collections. We then verify the resulting prediction model with the aid of a pregnant ewe and her foetus (Ovis aries) excavated in the Ptolemaic-Roman animal cemetery at Syene (modern Aswan, Egypt). Her condition illustrates that both the mother and her mature foetus must have died during birthing. Subsequently, we apply the model to humeri of very young archaeological sheep (Ovis orientalis/O. aries) unearthed at early Neolithic Aşıklı Höyük (Central Turkey). Both study cases underscore the practicality of our approach whilst illustrating the cultural and historical importance of precise age determinations in foetal, newborn and infantile sheep. Finally, we discuss the possible causes for foetal and neonatal mortality in sheep at Aşıklı Höyük.