Nutritional requirements and human evolution: A bioenergetics model

Abstract

A bioenergetics model is developed to examine changes in metabolic requirements over the course of human evolution. Data on (1) body size and resting metabolism, (2) brain size and metabolism, (3) activity budgets, and (4) foraging patterns for humans and other anthropoids are used to evaluate ecological correlates of variation in diet and energy expenditure. Analyses of variation in these extant species provide a framework for estimating (1) resting metabolic requirements, (2) brain metabolic needs, and (3) total energy requirements in fossil hominids. Anthropoid primates spend about 8% of resting metabolism to maintain their brains, a significantly larger proportion than in other mammals (3-4%), but still significantly less than 20-25% in humans. Total energy expenditure among anthropoids is positively correlated with day range and dietary quality. Human foragers fit this pattern, having high levels of energy expenditure, large foraging ranges, and a high quality diet. Within the fossil record, it appears that both total energy expenditure (TEE) and energy required by the brain increased substantially with the emergence of Homo erectus. For H. erectus, the percentage of resting metabolism used by the brain falls beyond the nonhuman primate range and approaches the modern human range. Additionally, TEE is 35-55% greater than in the australopithecines. The high total metabolic needs and the large proportion of energy required by the brain imply that important dietary changes occurred with H. erectus. These metabolic and dietary changes are linked to (1) the emergence of hunting and gathering, (2) the evolution of the human pattern of prolonged development, and (3) the coexistence and competition with the robust australopithecines.

Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution

“…Although several authors have pointed out that increasing M BR has energetic consequences (10)(11)(12)(13)(14)(15)(16)(17)23), it remained to be determined whether these would indeed be physiologically relevant to the extent of actually making metabolic cost a limiting factor in brain evolution. By using a simple model of scaling of energetic intake and expenditure with increasing M BD and number of brain neurons, here we demonstrate that, for primates feeding exclusively on a raw diet, metabolism is indeed a physiologically relevant limiting factor in evolution such that a tradeoff between M BD and number of brain neurons is imposed.…”

“…The brain is the third most energy-expensive organ in the human body, ranking in total organ metabolic cost below only skeletal muscle and liver (9). Accordingly, several studies have suggested that the main constraints to increasing primate brain size in evolution are metabolic in nature (10)(11)(12)(13)(14)(15)(16)(17)(18). The human brain, in particular, has come to cost ∼20% of the total body resting metabolic rate, even though it represents only 2% of total body mass (M BD ), whereas, in other primates, the brain consumes a lower percentage of the body resting metabolic rate of approximately 9% (17).…”

Body composition and resting metabolic rate of Japanese college Sumo wrestlers and non-athlete students: are Sumo wrestlers obese?

“…The average PAL of paleolithic humans was estimated to be approximately 1.8 (range 1.6-2.0: Leonard and Robertson, 1992;Cordain et al, 1998). Based on these epidemiological and paleolithic data, Yamauchi et al concluded that it is reasonable to consider a PAL of 1.75-1.80 as the desired level of daily physical activity (Yamauchi et al, 2004).…”

Addressing the wild yam question: how Baka hunter-gatherers acted and lived during two controlled foraging trips in the tropical rainforest of southeastern Cameroon

“…According to FAO (2001), a lifestyle with a PAL value of 1.70-1.99 is classified as an active or moderately active lifestyle, and that of 2.00-2.40 as a vigorous or vigorously active lifestyle. Leonard and Robertson (1992), who studied the bioenergetics of primates from the evolutionary viewpoint, described the PAL values of two hunter-gatherer groups as 1.71 for males and 1.51 for females of the !Kung and 2.15 for males and 1.88 for females of the Ache. The PAL value of the Baka is higher than that of the !Kung and seems to be comparable to that of the Ache.…”