Summary: I estimate, for humans and the most common domestic land animal livestock populations, their absolute and relative contributions to the total brain mass of the combined category. Humans make up the vast majority of the aggregate of brain mass for these populations, followed by cows. Chickens account for less than 1% of the total neural tissue of humans and domestic land animal livestock. As a proportion of the total number of neurons across these populations, cows and chickens are closer, due to the relatively high neuron density of chickens and humans, while the human proportion is higher.
