Meat-eating was an important factor affecting early hominin brain expansion, social organization and geographic
movement. Stone tool butchery marks on ungulate fossils in several African archaeological assemblages demonstrate a
significant level of carnivory by Pleistocene hominins, but the discovery at Olduvai Gorge of a child’s pathological cranial
fragments indicates that some hominins probably experienced scarcity of animal foods during various stages of their life
histories. The child’s parietal fragments, excavated from 1.5-million-year-old sediments, show porotic hyperostosis, a
pathology associated with anemia. Nutritional deficiencies, including anemia, are most common at weaning, when children
lose passive immunity received through their mothers’ milk. Our results suggest, alternatively, that (1) the developmentally
disruptive potential of weaning reached far beyond sedentary Holocene food-producing societies and into the early
Pleistocene, or that (2) a hominin mother’s meat-deficient diet negatively altered the nutritional content of her breast milk
to the extent that her nursing child ultimately died from malnourishment. Either way, this discovery highlights that by at
least 1.5 million years ago early human physiology was already adapted to a diet that included the regular consumption of
meat.