Eusociality is a cooperative living arrangement in which members of a species give up their own chances of reproduction to help raise the offspring of others. Traditionally, researchers have thought that eusociality arises through “kin selection theory.” Members of the group who give up their own reproduction to help others aren’t really altruistic; by helping their kin—who are genetically similar—they are actually favoring their own genes indirectly. With evolutionary biologist E.O. Wilson and mathematical biologist Corina Tarnita, Martin has come up with an alternative explanation: They argue that natural selection alone can explain the evolution of eusocial behavior through a number of steps. If a species follows these steps—its members stick together and develop the traits and genes that cause them to cooperate—eusociality is the result.