WHY THE BRAIN IS WRINKLED

THE BRAIN FOLDS IN ON ITSELF TO CRAM IN MORE PROCESSING POWER. The folds and pockets of our brains are a biological rarity that we only share with a few other species, including dolphins, some primates and elephants. It’s a clever evolutionary adaptation that allows intelligent species to squash a huge amount of cortical tissue into a small space, allowing enormous brainpower to be crammed into our relatively small skulls.

Folding starts during the second trimester of pregnancy, creating ridges (gyri) and fissures (sulci), but the biology behind the distinctive wrinkles is stranger than you might think. The organisation of the brain is determined by complex cascades of chemical signals, but the overall shape seems to be the result of simple physics. Grey matter sits on the outside of the brain and, during development, its growth rapidly outpaces the growth of white matter underneath. This puts mechanical stress on the structure, forcing the outside to buckle and curl. More wrinkled brains are associated with higher intelligence. (Brain sizes not to scale, obviously!)