By Lila Cart; Illustration by Daniela Gamba

Gorillas are estimated to have the second largest number of cortical neurons at 8-9 billion. Humans have 16 billions cortical neurons, nearly double the amount of gorillas. Gorilla brains (500 g) are about 1/3 size of human brains (1,500 g) despite their much larger body size.

Human brains follow the same scaling rules as other primates, meaning we have the expected number of neurons and brain size for a primate our size. This means that humans are not outliers by having a large brain. Instead, great apes, like gorillas and orangutans, may have evolved bodies too big to sustain larger brains. Large body size and brains with large numbers of neurons are both very costly. There are limits on amount of time that an animal can spend foraging. In turn, this means that there is a limited number of calories an animal can consume per day. Human ability to sustain large brains may have come from our ability to cook food with fire, which makes nutrients more readily available.


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