For creatures like us, evolution smiled upon those with a strong need to belong. Survival and reproduction are the criteria of success by natural selection, and forming relationships with other people can be useful for both survival and reproduction. Groups can share resources, care for sick members, scare off predators, fight together against enemies, divide tasks so as to improve efficiency, and contribute to survival in many other ways. In particular, if an individual and a group want the same resource, the group will generally prevail, so competition for resources would especially favor a need to belong. Belongingness will likewise promote reproduction, such as by bringing potential mates into contact with each other, and in particular by keeping parents together to care for their children, who are much more likely to survive if they have more than one caregiver.