Abstract
What makes humans unique? This question has fascinated scientists and philosophers for centuries and it is still a matter of intense debate. Nowadays, human brain expansion during evolution has been acknowledged to explain our empowered cognitive capabilities. The drivers for such accelerated expansion remain, however, largely unknown. In this sense, studies have suggested that the cooking of food could be a pre-requisite for the expansion of brain size in early hominins. However, this appealing hypothesis is only supported by a mathematical model suggesting that the increasing number of neurons in the brain would constrain body size among primates due to a limited amount of calories obtained from diets. Here, we show, by using a similar mathematical model, that a tradeoff between body mass and the number of brain neurons imposed by dietary constraints during hominin evolution is unlikely. Instead, the predictable number of neurons in the hominin brain varies much more in function of foraging efficiency than body mass. We also review archeological data to show that the expansion of the brain volume in the hominin lineage is described by a linear function independent of evidence of fire control, and therefore, thermal processing of food does not account for this phenomenon. Finally, we report experiments in mice showing that thermal processing of meat does not increase its caloric availability in mice. Altogether, our data indicate that cooking is neither sufficient nor necessary to explain hominin brain expansion.
Highlights
Human evolution is marked by a significant increase in the total brain size relative to body size, referred to as encephalization
Studies on human brain evolution have been largely based upon two main lines of evidence: (i) fossil records, termed paleoneurology; and (ii) indirect evidence coming from anatomical, physiological, and behavioral comparison between humans and closely related extant primates, such as chimpanzee
Cooking and Human Brain Evolution hominins, comparisons between existing primates permit a more detailed analysis on how gross and microscopic organization of the brain correlates with different behaviors, allowing some inferences about anatomic and functional aspects of the brain
Summary
Human evolution is marked by a significant increase in the total brain size relative to body size, referred to as encephalization. Studies on human brain evolution have been largely based upon two main lines of evidence: (i) fossil records, termed paleoneurology; and (ii) indirect evidence coming from anatomical, physiological, and behavioral comparison between humans and closely related extant primates, such as chimpanzee. While the former allows inferences about the total brain volume of extinct. The combination of direct and indirect evidence is mandatory to develop a better understanding of when and how the human brain evolved Based on such “direct” and “indirect” evidence, many different theories have been proposed to explain the disproportionate growth of the brain in the human lineage, considering the high energetic cost of larger brains (Mink et al, 1981). We show that large primate encephalization was reached millions of years before the widespread control of fire, a pre-requisite for cooking, and provide evidence indicating that early hominins were likely to obtain enough calories from raw meat to afford for the size of their brains
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