In the spring of 1973, the Baharvand tribe from the Luristan province of central western Iran prepared to migrate from their winter pastures to their summer camp in the mountains. Seasonal migration in spring and fall had been their way of life for as long as anyone in the camp could remember. They moved their camp and their animals--sheep, goats, horses, donkeys, and chickens--in order to find green pastures and suitable temperatures. That year,...