The Japanese Macaca monkey has been studied in the wild for over 50 years. In 1952, on one small Japanese island, scientists dropped some
1dirt for the monkeys. The monkeys liked their taste, but they found the dirt
2.
One clever 18-month-old monkey
3 the problem by washing the sweet potatoes in a nearby river, She taught this to her mother. Her
4also learned this new way and they taught their mothers too.
All the younger monkeys
5 learned to wash the dirty sweet potatoes to make them
6 to eat. But many found it very hard to learn this and still ate the
7 sweet optatoes.
Then something very
8 . In the autumn of 1958, scientists found that the monkeys on other nearby
9began washing their sweet potatoes too. Scientists still don't fully understand how this knowledge was
10from one island to another.
