Pronghorn antelope are the fastest runners in North America, clocked at speeds of up to 100 kilometers per hour. Yet none of their current predators can come close to running this fast. Pronghorn also gather in groups, a behavior commonly viewed as a "safety in numbers" defense. But again, none of their living predators are fearsome enough to merit such a response. In this elegantly written book, John A. Byers argues that these mystifying behaviors...