100th Monkey Syndrome
A nice description of this interesting phenomenon.
The Japanese monkey, Macaca fuscata, had been observed in the wild for a period of over 30 years.
In 1952, on the island of Koshima, scientists were providing monkeys with sweet potatoes dropped in the sand. The monkey liked the taste of the raw sweet potatoes, but they found the dirt unpleasant.
An 18-month-old female named Imo found she could solve the problem by washing the potatoes in a nearby stream. She taught this trick to her mother. Her playmates also learned this new way and they taught their mothers too.