Estimating weaning and early childhood diet from serial micro-samples of dentin collagen

Age of weaning is an important measure of parental investment, and in various human and non-human primate studies, has been correlated with a range of developmental factors such as stature, cognitive functions, obesity, ability to cope with stress, and rates of disease. Archaeological estimation of the weaning process is generally at the level of an entire burial population, creating some challenges in using such data to test anthropological theory. We describe a method that tracks the weaning process at the individual level, based on the measurement of stable nitrogen and carbon isotope ratios in serial sections of first molar dentin collagen. We apply this micro-sampling technique to a sample of individuals from CA-CCO-548, a well-studied and ancient site on the banks of Marsh Creek in Central California. Results show great variation between individuals in both the length of the weaning process, the age at which breastfeeding stopped, and the source of early complementary childhood foods.