Research press release



Evolution: Faster metabolism enabled big human brains



今回、Herman Pontzerたちは、ヒトの大型サンプル(141人)と既知の大型類人猿全種を対象としてエネルギー消費量を直接測定し、アーカイブデータの再検討も行った。その結果、ヒトの代謝率が増加し、エネルギー収支も大きくなり、1日当たりの総エネルギー消費量(TEE)が、チンパンジーとボノボより400 kcal、ゴリラより635 kcal、オランウータンより820 kcalそれぞれ多いことが判明した。そして、ヒトのTEE増加は、基礎代謝率の増加によるところが大きいと考えられ、ヒトの臓器での代謝活性が亢進したことが示されているとPontzerたちは述べている。基礎代謝率は、安静時の身体機能を維持するために必要なエネルギー量のことで、kcal/日で測定される。さらに、Pontzerたちは、ヒトの体脂肪率が他の霊長類よりかなり高いことを明らかにし、これがTEEの増加と共進化してエネルギー要求量の増加という固有のリスクが軽減されたという考えを示している。

Humans evolved their relatively large brain, compared to other primates, thanks to an increased metabolic rate, reports a paper published in Nature. The study also suggests that humans may have evolved a much higher body fat percentage than other primates to provide the energy reserves required to fuel their more extensive metabolism.

Humans are different from other primates in that they live longer, breed more, have more body fat, relatively smaller guts, and relatively large brains. These traits are metabolically expensive, which suggests there are significant differences in energy expenditure and allocation between humans and apes. However, the mechanisms underlying these differences have remained unknown.

Herman Pontzer and colleagues took direct measurements of daily energy expenditure in large samples of humans (141 people) and all known species of great ape, as well as revisiting archival data. They show that humans have evolved a faster metabolism and larger energy budget, with total energy expenditure (TEE) greater than that of chimpanzees and bonobos, gorillas, and orangutans by approximately 400, 635 and 820 kcal per day, respectively. They find that much of the increase in TEE is attributable to humans’ greater basal metabolic rate - the amount of energy required to keep the body functioning at rest, measured in kcal per day - which indicates increased metabolic activity in their organs. Finally, the authors show that humans evolved a much higher body fat percentage than other primates, and suggest that this coevolved with greater TEE to mitigate the inherent risk of increased energy demands.

doi: 10.1038/nature17654|英語の原文

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