The size of the human brain has roughly tripled over the past four million years of hominid evolution, yet the factors driving this encephalic expansion are not fully understood. Attempting to solve this conundrum, a very brainy biologist has devised a computer model that recreates the development of our cognitive contraption, revealing that the human cerebrum may owe its size to our pattern of sexual maturation.
[W]hile it is often posited that an evolutionary arms race pushes species towards higher cognitive capacities and therefore bigger brains, [Mauricio González-Forero, from the University of St Andrews] states that “the arms races fail to yield evolutionarily stable human-sized brains and bodies given their metabolic costs.”
In other words, growing a brain comes at a price and restricts the amount of energy available for the development of other tissue types. Under the arms race scenario, therefore, it would have been impossible for our species to develop such a large brain while also enjoying such magnificent bodies.
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Beginning with Australopithecus afarensis – the species to which the famous Lucy belongs – and continuing all the way through to Homo sapiens, González-Forero reveals that brain size is always dependent upon the age of sexual maturation. More specifically, as the age of sexual development increases, so too does the size of the brain.
