Your recent article about the diverse people's who populated early South America gave short shrift to an important ancient culture. The Moche people inhabited the river valleys and coastal plain of northern Peru between AD 100 and AD 800. You rightly note that archaeologists are elated by recent discoveries in the region: The sophisticated Moche built pyramids, temples, and irrigation canals and produced extraordinary ceramics and murals. Yet the article offers no trenchant explanation for why the Moche"disappeared.