Brains might be the most complex structures on our planet—so how did evolution build them? To find out, rewind the clock three billion years to trace the evolutionary story of the dolphin, one of the smartest animals alive today. Discover how the first light sensing cells led to eyes that helped wire bodies to think, how a fluke viral infection supercharged the speed of thought, and how the neocortex emerged as early mammals re-wired their brains to attune to the night. Together, these breakthroughs reveal how evolution transformed simple perception into the most powerful organ on Earth—a structure capable of thought, communication, and empathy.