In 1758 the Swedish taxonomist Carolus Linnaeus dubbed our species Homo sapiens, Latin for “wise man.” It’s a matter of open debate whether we actually live up to that moniker. If Linnaeus had wanted to stand on more solid ground, he could have instead called us Homo megalencephalus: “man with a giant brain.”
Regardless of how wisely we may use our brains, there’s no disputing that they are extraordinarily big. The average human brain weighs in at about three pounds, or 1,350 grams. Our closest living relatives, the chimpanzees, have less than one-third as much brain—just 384 grams. And if you compare the relative size of brains to bodies, our brains are even more impressive.
As a general rule, mammal species with big bodies tend to have big brains. If you know the weight of a mammal’s body, you can make a fairly good guess about how large its brain will be. As far as scientists can tell, this rule derives from the fact that the more body there is, the more neurons needed to control it. But this body-to-brain rule isn’t perfect. Some species deviate a little from it. A few deviate a lot. We humans are particularly spectacular rule breakers. If we were an ordinary mammal species, our brains would be about one-sixth their actual size.
