Mammals and birds have dramatically more neurons in their forebrain and cerebellum than reptiles, and neuron numbers have scaled up significantly only four times in more than 300 million years of brain evolution in the clade that includes reptiles, birds, and mammals, according to a study published in PNAS on March 7. Instead of brain volume, which has long been used as a proxy for brain complexity, the study’s authors used the number of neurons typically found in species’ brains as an indicator of smarts.
“Reptile brains are smaller than the brains of birds or mammals of similar body size, but just how much smaller and how the size difference translates into differences in behavior and cognition is a problem that has eluded scientists for a long time,” Enrique Font, a zoologist and ethologist at the Universidad de Valencia in Spain who was not involved in the study, writes in ...
