Turtle hatchlings have, it seems, evolved to crawl toward the light. For millions of years this was a highly rational and effective strategy because the light on a dark beach represented the reflection of the moon and stars on the water's surface. Following the lights led baby turtles back home to the sea. The problems started when humans began building beachfront homes and sparkling hotels on the other side of the beach. Now after hatching, turtles heading for the brightest nearby lights were being guided straight into traffic. Are self-destructive sea turtles naturally irrational? Yes, in the modern world. But there's a deeper truth. Turtles are basing their decisions on simple cues that were perfectly rational for their ancestors; these days, however, their evolved decision‐making mechanisms are being blinded by modern lights.