Self-Interest and the Design of Rules Manvir Singh 1 & Richard Wrangham 1 & Luke Glowacki 1,2 Published online: 24 August 2017 # Springer Science+Business Media, LLC 2017, Corrected publication September/2017 Abstract Rules regulating social behavior raise challenging questions about cultural evolution in part because they frequently confer group-level benefits. Current multi- level selection theories contend that between-group processes interact with within- group processes to produce norms and institutions, but within-group processes have remained underspecified, leading to a recent emphasis on cultural group selection as the primary driver of cultural design. Here we present the self-interested enforcement (SIE) hypothesis, which proposes that the design of rules importantly reflects the relative enforcement capacities of competing parties. We show that, in addition to explaining patterns in cultural change and stability, SIE can account for the emergence of much group-functional culture. We outline how this process can stifle or accelerate cultural group selection, depending on various social conditions. Self-interested enforcement has important bearings on the emergence, stability, and change of rules. Keywords Cultural evolution . Social evolution . Norms . Institutions . Self-interested enforcement Rules are ubiquitous, influential, and numerous in human social life. Among the Kapauku Papuans, Pospisil (1958a) documented 120 rules pertaining to murder, assault, food taboos, the appropriate context for lying, deference toward authority, inheritance, incest taboos, and property rights. Pospisil’ s list represented Kapauku “law” only, excluding such central institutions as the customs surrounding birth or adoption, or the many informal norms enabling the coordination of social life. In a study of Malagasy taboos, Ruud (1960) identified more than 600 prohibitions and prescriptions, including 48 concerning the consumption and treatment of plants, 94 Hum Nat (2017) 28:457–480 DOI 10.1007/s12110-017-9298-7 * Manvir Singh manvirsingh@fas.harvard.edu 1 Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA 2 Institute for Advanced Study in Toulouse, Toulouse, France