The Four Horsemen of the Apocalypse

Darwin: Once we have the capacity to sympathize with others, there's nothing that can prevent it from expanding to encompass the entire human species. "As soon as I have to negotiate agreements in larger circles of individuals, I'm forced to expand my circle of sympathy outward," he says. The four horsemen of the apocalypse -- war, pestilence, famine and death -- will be revealed at the end of this century.