Throughout centuries, the fortunes of China's ancient kingdoms rose and fell with monsoon cycles, a new study suggests.

The discovery is based on a nearly 2,000-year-old record of monsoon activity recently discovered in a cave.

Monsoon winds carry rain-laden clouds through China every summer, providing nearly 80 percent of the annual precipitation in some parts of the country.

When the winds are weak, little to no rain reaches large expanses of China, often plunging those areas into drought.

The new study "is a brilliant analysis of the problematic coincidence of abrupt climate changes and changes in political organization," said Harvey Weiss, an archaeologist at Yale University who was not involved in the study...   more »