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.
This cultural innovation was gradually picked up by various monkeys before the eyes of the scientists. Between 1952 and 1958 all the young monkeys learned to wash the sandy sweet potatoes to make them more palatable.Only the adults who imitated their children learned this social improvement. Other adults kept eating the dirty sweet potatoes.
Then something startling took place. In the autumn of 1958, a certain number of Koshima monkeys were washing sweet potatoes -- the exact number is not known. Let us suppose that when the sun rose one morning there were 99 monkeys on
THEN IT HAPPENED!