On December 26, 2004, a massive tsunami triggered by an underwater earthquake pummeled the coasts of Thailand, Indonesia, Sri Lanka, and other countries along the Indian Ocean. With casualties as far away as Africa, the aftermath was overwhelming: ships could be spotted miles inland; cars floated in the ocean; legions of the unidentified dead-an estimated 225,000-were buried in mass graves; relief organizations struggled to reach rural areas and provide adequate aid for survivors. Shortly after this disaster, researchers from around the world traveled to the region's most devastated areas,...