Brain evolution

Mammalian brain evolution has too often been studied with the implicit assumption that all mammalian brains were made according to the same scaling rules. Our lab has shown that this is not the case, as the relationship between the size of brain structures and their numbers of neurons varies both across mammalian orders and structures.

The illustration below (from Herculano-Houzel, 2012) illustrates that large brain size has evolved several times independently from a common ancestor that had a small brain. There is, therefore, no a priori reason to assume that all brains that have become large did so through the same mechanisms in evolution.