Contraintes énergétiques et nutritionnelles sur le développement du cerveau : implications pour l'expansion du cerveau humain au cours de son évolution

The developing human brain has a very high energy requirement, and a need for specific brain selective nutrients. By inference, these energetic and nutritional constraints for normal brain development today would also have been constraints on human brain evolution. The energetic constraint was solved mainly by the evolution of a significant layer of body fat in the fetus during the third trimester of gestation. By providing fatty acids for ketone production that are essential brain fuels during development, this fat layer supports the brain's high energy needs well into childhood. This fat layer also provides a significant supply of the brain selective omega-3 fatty acid-docosahexaenoic acid (DHA). Neither this fat layer nor this DHA reserve are available in other primates. Brain selective minerals, particularly, iodine and iron, with zinc, copper and selenium are also important for normal brain development. A shore-based diet, i.e. fish, molluscs, crustaceans, frogs, bird's eggs and aquatic plants, provides the richest known dietary sources of DHA and brain selective minerals. Access to these foods by the early hominin lineage that evolved into humans would have helped overcome the nutritional constraint on primate brain development and function. The “shore-based paradigm” of human brain evolution proposes that sustained access by certain groups of early Homo to freshwater and marine food resources would have helped surmount both the nutritional as well as the energetic constraints on mammalian brain development. The brain's ongoing developmental vulnerability to an inadequate dietary supply of brain selective nutrients still has a deleterious impact on human brain development on a global scale today.