Insights into the palaeobiology of an early Homo infant: multidisciplinary investigation of the GAR IVE hemi-mandible, Melka Kunture, Ethiopia

International audience; Childhood is an ontogenetic stage unique to the modern human life history pattern. It enables the still dependent infants to achieve an extended rapid brain growth, slow somatic maturation, while benefitting from provisioning, transitional feeding, and protection from other group members. This tipping point in the evolution of human ontogeny likely emerged from early Homo. The GAR IVE hemi-mandible (1.8 Ma, Melka Kunture, Ethiopia) represents one of the rarely preserved early Homo infants (~ 3 years at death), recovered in a richly documented Oldowan archaeological context. Yet, based on the sole external inspection of its teeth, GAR IVE was diagnosed with a rare genetic diseaseamelogenesis imperfecta (AI)-altering enamel. Since it may have impacted the child's survival, this diagnosis deserves deeper examination. Here, we reassess and refute this diagnosis and all associated interpretations, using an unprecedented multidisciplinary approach combining an in-depth analysis of GAR IVE (synchrotron imaging) and associated fauna. Some of the traits previously considered as diagnostic of AI can be better explained by normal growth or taphonomy, which calls for caution when diagnosing pathologies on fossils. We compare GAR IVE's dental development to other fossil hominins, and discuss the implications for the emergence of childhood in early Homo. The pattern and timing of modern human life history is unique in involving an extended period of growth 1. This provides more time not only for somatic development and protracted brain growth 2, 3 , but also to learn survival skills 4. The offspring is thus dependent upon more parental care over a longer time, and sexual maturity is postponed 5. In modern humans, life history stages successively involve infancy, childhood, a juvenile phase, adolescence, and finally adulthood. Different kinds of feeding strategies and dental development stages characterize these phases. Following these criteria, infancy can be subdivided into two stages. First, the "nursing phase" takes place from birth to 6 months, when the infant exclusively relies on breastfeeding and starts erupting its