Evolution of division of labor: Emergence of different activities among group members Wataru Nakahashi a,n , Marcus W. Feldman b a School of Advanced Sciences, The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa 240-0193, Japan b Department of Biology, Stanford University, Stanford, CA 94305, USA HIGHLIGHTS  We investigate under what conditions division of labor (DL) should evolve.  DL likely evolves when group size is large and skill learning is important.  DL also likely evolves when there is food sharing within a group.  DL by gender likely evolves when the difference between genders is large.  We discuss the evolution of DL in hominids. article info Article history: Received 29 August 2013 Received in revised form 16 January 2014 Accepted 21 January 2014 Available online 28 January 2014 Keywords: Social system Learning strategy Evolutionarily stable strategy (ESS) Evolutionary branching abstract The division of labor is an important component of the organization of human society. However, why this division evolved in hominids requires further investigation. Archeological evidence suggests that it appeared after the emergence of Homo sapiens and contributed to the great success of our species. We develop a mathematical model to investigate under what conditions division of labor should evolve. We assume two types of resources the acquisition of which demands different skills, and study the evolution of the strategy that an individual should use to divide its lifetime into learning and using each skill. We show that division of labor likely evolves when group size is large, skill learning is important for acquiring resources, and there is food sharing within a group. We also investigate division of labor by gender under the assumption that the genders have different efficiencies in acquiring each resource. We show that division of labor by gender likely evolves when skill learning is important and the difference in efficiencies between genders in acquiring resources is large. We discuss how the results of our analysis might apply to the evolution of division of labor in hominids. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction The division of labor within groups of hominids, e.g., modern humans, is an important component of the organization of human society. For example, in the recent past hunter–gatherers have generally divided their labor by gender and age, i.e., men hunt, women and children gather (Dahlberg, 1975; Marlowe, 2010), although there are some exceptions (Estioko-Griffin and Griffin, 1981). Agricultural and industrial societies have more complex divisions of labor. Some insect societies also appear to have division of labor (Gordon, 1999). However, why such divisions evolved remains to be explained. Although studies of division of labor have a long history in economics, business, and sociology (e.g., Smith, 1776; Marx, 1867), they have mainly discussed the most efficient division of labor and have not taken an evolutionary perspective. Since natural selection acts on individuals, not groups (although group selection may some- times occur), we should consider the fitness of individuals when we address the evolution of division of labor, especially its emergence in hominids. Since the fitness of each individual is affected by others’ strategies in the context of social behaviors, evolutionary game theory provides a useful approach to this problem. In modeling the evolution of hominid division of labor, we attempt to take anthropological evidence into consideration. The division of labor is composed of three factors, the formation of a group, food (resource) sharing within a group, and different activities among group members. Taking anthropological evidence into account, let us explore when each factor might have evolved in hominids. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/yjtbi Journal of Theoretical Biology 0022-5193/$ - see front matter & 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jtbi.2014.01.027 n Corresponding author. Tel.: þ81 46 858 1580. E-mail address: w.nakahashi@gmail.com (W. Nakahashi). Journal of Theoretical Biology 348 (2014) 65–79