Thank you for an inspiring read. Here’s one hypothesis for the natural selection of eyebrows. Homo sapiens shed all of their hair and kept only those that allowed utility and communication. Thinning mop of hair to keep the brain cool. Eyebrows to allow communication; how else could you read a child’s emotions if he is covered in hair? But what about armpits, groins and mustaches? Perhaps in men, it is to hide men’s emotions behind a lumberjack’s beard.