First human ancestors breastfed for longer than contemporary relatives

By analysing the fossilised teeth of some of our most ancient ancestors, a team of scientists led by the universities of Bristol (UK) and Lyon (France) have discovered that the first humans significantly breastfed their infants for longer periods than their contemporary relatives. The results, published in the journal Science Advances , provide a first insight into the practice of weaning that remain otherwise unseen in the fossil record. The team sampled minute amounts from nearly 40 fossilised teeth of our South African fossil relatives, early Homo , Paranthropus robustus and Australopithecus africanus . They measured the proportions of their stable calcium isotopes in the tooth enamel, which are a function of the mother milk intake by infants. By reconstructing the age at tooth enamel development, they show that early Homo offspring was breastfed in significant proportions until the age of around three to four years, which likely played a role in the apparition of traits that are specific to human lineage, such as the brain development. In contrast, infants of Paranthropus robustus , that became extinct around one million years ago and were a more robust species in terms of dental anatomy, as well as infants of Australopithecus africanus , stopped drinking sizeable proportions of mother milk in the course of the first months of life. These differences in nursing behaviours likely come with major changes in the social structures of groups as well as the time between the birth of one child and the birth of the next.