Metabolic acceleration and the evolution of human brain size and life history

Abstract

Humans are distinguished from the other living apes in having larger brains and an unusual life history that combines high reproductive output with slow childhood growth and exceptional longevity1. This suite of derived traits suggests major changes in energy expenditure and allocation in the human lineage, but direct measures of human and ape metabolism are needed to compare evolved energy strategies among hominoids. Here we used doubly labelled water measurements of total energy expenditure (TEE; kcal day−1) in humans, chimpanzees, bonobos, gorillas and orangutans to test the hypothesis that the human lineage has experienced an acceleration in metabolic rate, providing energy for larger brains and faster reproduction without sacrificing maintenance and longevity. In multivariate regressions including body size and physical activity, human TEE exceeded that of chimpanzees and bonobos, gorillas and orangutans by approximately 400, 635 and 820 kcal day−1, respectively, readily accommodating the cost of humans' greater brain size and reproductive output. Much of the increase in TEE is attributable to humans' greater basal metabolic rate (kcal day−1), indicating increased organ metabolic activity. Humans also had the greatest body fat percentage. An increased metabolic rate, along with changes in energy allocation, was crucial in the evolution of human brain size and life history.

The evolutionary roles of nutrition selection and dietary quality in the human brain size and encephalization

“…These larger territorial needs for humans appear to be associated with larger daily energy budgets. Recent work by Pontzer and colleagues [30,31] has shown that humans are indeed the "high energy" apes. Using the doubly labeled water (DLW) technique to quantify total daily energy expenditure (TEE; kcal/day), they have shown that humans have systematically and significantly greater energy budgets than chimpanzees, gorillas, or orangs.…”

The costs of a big brain: extreme encephalization results in higher energetic demand and reduced hypoxia tolerance in weakly electric African fishes

“…Extreme encephalization, where brain size greatly deviates from a lineage's allometric relationship between brain and body mass, is rare [14]. In studies of highly encephalized primates, both hypotheses are hotly debated [10], with some studies favouring the direct metabolic constraints hypothesis [5,9], and others favouring the energetic trade-off hypothesis [6,15]. Further, due to a lack of comparative studies of & 2016 The Author(s) Published by the Royal Society.…”

Relationship between Various Food Uptakes and Body Mass Index (BMI) in Japanese Young and Old Men and Women

“…Recently, it has been proposed that calorie expenditures of human beings are similar regardless of the extent of physical activity [16,17]. Although exercise is very important for human health, exercise is not an effective measure of reducing weight.…”