Implications of Brain Evolution in Cetaceans and Primates for Highly Intelligent Extraterrestrial Life

There are stars and Earth-like planets believed to be over 10 billion years in age. “Water worlds” and moons that contain salty oceans may be commonplace in this galaxy. The evolution of cetaceans and primates may provide some clues as to how intelligent life may have evolved on other planets. The most intelligent species of primate, Homo sapiens, has an average brain mass (~1350 g) that is considerably larger than any of the other primates but much smaller than the averages for many cetaceans, which are also believed to be very intelligent. The factors that led a subset of primates rather than the comparatively huge-brained cetaceans to dominate (from a human perspective) our planet are reviewed, including language and tool making capability. If intelligent cetacean-like beings evolved convergently in other worlds in response to aquatic habitats similar to Earth's, they would not be expected to have complex tools and technologies, whereas primate-like beings that may have evolved convergently on other planets that are much older than Earth might have long ago developed technologies that surpass our own.