Diet and Brain Evolution: Nutritional Implications of Large Human Brain Size


Summary Points on Diet and Human Brain Evolution: • Humans expend a much larger share of their resting energy budget on brain metabolism than other species. Adult humans spend 20–25% of the RMR on the brain, as compared to 8–10% in other primates, and 3–5% in non-primate mammals. • To support the high energy costs of brain metabolism, humans consume diets that are easier to digest and much more dense in energy and fat than other primate species. • The first major increase in brain size in the human lineage occurred with the evolution of the genus Homo at 2.0–1.7 million years ago. During this time, we also have evidence from the fossil and archaeological record for greater consumption of animal foods. This increased dietary quality was likely important for supporting brain evolution. • The addition of animal foods to the diet of early Homo would also have increased the availability of key long-chain polyunsaturated fatty acids that are essential for brain growth and development: DHA and AA. • For human infants, the energy costs of brain metabolism are extraordinarily high (<60% of RMR) due to high brain to body weight ratios and rapid brain growth. These costs are supported, in part, by very high levels of body fatness. At 15–16% fat, humans have the fattest infants of any mammal. • Under conditions of chronic nutritional and disease stress, human infants “downregulate” growth in length/stature, while preserving body fatness. This pattern of “linear growth stunting” is widely observed among impoverished populations of the developing world, and appears to be associated with reduced fat oxidation and increased fat storage. • Ongoing research is attempting to better characterize the dietary patterns of our earliest human ancestors through chemical analyses of hominin bones and analyses of microscopic wear patterns of hominin teeth.


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