title: The evolution of reciprocity in sizable human groups.
abstract: The scale and complexity of human cooperation is an important and unresolved evolutionary puzzle. This article uses the finitely repeated n person Prisoners' Dilemma game to illustrate how sapience can greatly enhance group-selection effects and lead to the evolutionary stability of cooperation in large groups. This affords a simple and direct explanation of the human "exception".
authors.affiliation: Department of Economics, Middlebury College, VT 05753, USA. caseyr@mit.edu
authors.forename: Casey G
authors.initials: CG
authors.lastname: Rothschild