It is common for us to focus on the competitive aspects of the well-worn phrase “survival of the fittest.” As it turns out, however, we sell nature short when we do so. Fitness is not simply a cutthroat matter of outperforming others to survive and reproduce--thus passing along those successful genes. As you will learn in this issue's cover story, “ Why We Help ,” by Martin A. Nowak, cooperation among members of groups, from single-celled amoebas to the complex assemblages found in mammals, has helped shape the evolution of all of life on earth in profound ways. Individuals may engage in various flavors of cooperation, from discharging a beneficial duty for kin to performing selfless actions for the greater good. It may (or may not) surprise you to learn that people earn a unique place among species as the most mutually helpful of all. Nowak calls the phenomenon the “snuggle for survival.” For more, turn to page 34.