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