ST LOUIS, MISSOURI—Excavations at the Sanyangzhuang site and the Anshang site along China’s lower Yellow River flood plain, and analysis of sedimentary soils deposited along the Yellow River over thousands of years, indicate that people were changing the environment nearly 3,000 years ago. “Human intervention in the Chinese environment is relatively massive, remarkably early, and nowhere more keenly witnessed than in attempts to harness the Yellow River,” archaeologist T.R. Kidder announced at Washington University. The large-scale levees and other flood-control systems, such as those at the Anshang site, are thought to have made periodic flooding much worse, including a catastrophic flood circa A.D. 14-17 that buried the Sanyangzhuang site and may have triggered the collapse of the Western Han Dynasty. “Our evidence suggests that the first levees were built to be about 6-7 feet high, but within a decade the one at Anshang was doubled in height and width. It’s easy to see the trap they fell into: building levees causes sediments to accumulate in the river bed, raising the river higher, and making it more vulnerable to flooding, which requires you to build the levee higher, which causes the sediments to accumulate, and the process repeats itself. The Yellow River has been an engineered river—entirely unnatural—for quite a long time,” Kidder explained.