Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves

by James Nestor

The sperm whale’s brain, like its clicks, both distinguishes it from a human’s and suggests surprising similarities between the two species. Six times the size of the human brain and in many ways more complex, the sperm whale’s brain is the largest brain that’s ever existed on Earth, as far as we know. The inferior colliculus in the sperm whale brain, which helps sense pain and changes in temperature and serves as an auditory pathway from one area of the brain to the other, is twelve times larger than a human’s; its lateral lemniscus, which processes sound, is two hundred and fifty times the size of a human’s. The neocortex, the part of the brain that, in humans, governs higher-level functions such as conscious thought, future planning, and language, is estimated to be about six times larger in the sperm whale brain than it is in ours.