When a young snow monkey named Imo’ innovated cleaning her sweet potatoes by dipping them into the sea, the adults in her troop were slow to take notice. They lived together on a tiny islet in Japan, but only two adults in the troop copied her behavior over the next five years. The young monkeys, though, the other children and subadults, watched and learned. Five years on, nearly 80 percent of the juvenile monkeys were cleaning their sweet potatoes in the style of Imo’.