ABSTRACT
Humans form long-term attachments to others with whom they are close (Mikulincer & Shaver, 2007), empathize with others (Batson, 1998), and sacrifice their immediate self-interests to promote the overarching interests of the groups and communities to which they belong (Dawes, 1980; Komorita & Parks, 1995; Ostrom, 1998; Penner, Dovidio, Piliavin, & Schroeder, 2005). Their extraordinary capacity to create and maintain social life may take rather extreme forms—to promote a common cause, or to protect their group against enemy forces, humans may sacrifice their lives; for example, as soldiers or suicide bombers (Kruglanski, Chen, Deschesne, Fishman, & Orehek, 2009; Stouffer et al., 1949; Tobena, 2009). These and related observations fit the idea, however, that throughout evolution, pro-social behavior promotes the functioning of the individual’s in-group, which in turn provides for levels of security and prosperity well beyond what individuals could possibly achieve alone (Bowles & Gintis, 2011; Henrich, N. & Henrich, J., 2007).
