The Altruistic UrgeOrdinary people can perform acts of astonishing selflessness, sometimes even putting their lives on the line. A pregnant woman saw a dorsal fin and blood in the water and dove right in to pull her wounded husband to safety. Remarkably, some even leap into action to save complete strangers: one New York man jumped onto the subway tracks to rescue a boy who had fallen into the path of an oncoming train. Such behavior is not uniquely human. Researchers