Popular culture, based on scientific study, indicates that dolphins and whales are second only to humans in intelligence – but how true is this common perception? This talk will examine the behavioural, neuroanatomical and evolutionary evidence to delve into the world of the cetacean brain and arise at a different answer. Yes, the cetacean brain is specialized, but this is not to subserve complex cognition, rather it is specialized in several different specific ways that are all related to the production of heat. Cetaceans are under a substantial thermal pressure in their aquatic environment and therefore the brain must produce a great deal of heat to overcome this thermal pressure. It can be shown that during their evolutionary history oceanic temperatures played a crucial role in the evolution of a large brain and that the effect of oceanic temperatures is reflected in their current zoogeography and structure of the brain. This different understanding of cetacean brain structure, function and evolution, frees evolutionary neuroscience from the constraints of the cognitive imperative of large brain evolution and allows us to examine brain evolution from a range of new perspectives not related to the anthropomorphic view of intelligence.