Suzana Herculano-Houzel (1972-) The Human Advantage (2016)
A New Understanding of How Our Brain Became Remarkable
10. Brains or Brawn: You Can't Have Both
...Because an individual brain always uses the same amount of energy, no matter whether the rest of the body is starving, having too many neurons is clearly a liability when a species lives close to the limit of its caloric intake possibilities.
But for our newly bipedal and suddenly highly mobile australopithecine ancestor, who, some 4 million years ago, diverged away from the lineage that would give rise to the modern chimpanzee and bonobo, investing the additional kilocalories it amassed per day in a greater number of brain neurons housed in a leaner, lighter body must have proven a much better investment strategy. How, exactly, the great ape and human lineages came to adopt different investment strategies, privileging brawn over brains or brains over brawn can only be guessed at. What becomes clear, though, once energy requirements and availability are taken into consideration, is that one can't have both.
10. Brains or Brawn: You Can't Have Both
...Because an individual brain always uses the same amount of energy, no matter whether the rest of the body is starving, having too many neurons is clearly a liability when a species lives close to the limit of its caloric intake possibilities.
But for our newly bipedal and suddenly highly mobile australopithecine ancestor, who, some 4 million years ago, diverged away from the lineage that would give rise to the modern chimpanzee and bonobo, investing the additional kilocalories it amassed per day in a greater number of brain neurons housed in a leaner, lighter body must have proven a much better investment strategy. How, exactly, the great ape and human lineages came to adopt different investment strategies, privileging brawn over brains or brains over brawn can only be guessed at. What becomes clear, though, once energy requirements and availability are taken into consideration, is that one can't have both.