In the spring of 1959, Yang Jisheng, then an 18-year-old scholarship student at a boarding school in China's Hubei Province, got an unexpected visit from a childhood friend. "Your father is starving to death!" the friend told him. "Hurry back, and take some rice if you can."

Granted leave from his school, Mr. Yang rushed to his family farm. "The elm tree in front of our house had been reduced to a barkless trunk," he recalled, "and even its roots had been dug up." Entering his home, he...