What is it about?
Brain processing capacity, one of the factors contributing to intelligence, is best estimated by the number of neurons. Examining a large sample of species, we found that mammals and birds both converged on similar neuron numbers for brain mass, much higher than reptiles. Neurons use up a lot of energy and being warm-blooded might have tipped the balance in favour of more complex but costly brains. Additionally, primates and core landbirds (which include groups such as parrots, songbirds, and birds of prey) experienced another upward shift, increasing their brain size and neuron densities even further. This likely underlies their extraordinary cognitive abilities.
Photo by Hal Gatewood on Unsplash
Why is it important?
By looking directly at neuron numbers instead of brain size, we get a more accurate picture of the actual processing power. Knowing how brain capacity changes enables us to better understand the selection pressures shaping brain evolution.
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This page is a summary of: The evolution of brain neuron numbers in amniotes, Proceedings of the National Academy of Sciences, March 2022, Proceedings of the National Academy of Sciences,
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