This paradox has made deciphering the context in which such behavior would be favored a popular, but contentious, field of inquiry. Indeed, the study of the evolution of eusociality has been plagued by disagreements: over how to describe the

attributes of social groups (Crespi & Yanega, 1995; Gamma-secretase inhibitor Sherman et al., 1995); the level at which selection acts (Wilson, 1975; Foster, Wenseleers & Ratnieks, 2006); and the proper focus of fitness calculations (Taylor, Wild & Gardner, 2007). These arguments continue in the literature to this day (Nowak, Tarnita & Wilson, 2010; Abbot et al., 2011; Boomsma et al., 2011; Bourke, 2011). One challenge in evaluating alternative selective hypotheses for the evolution of eusociality is that eusociality is itself composed of multiple social traits, whose evolutionary history must be properly reconstructed in order to understand the conditions in which they evolved. Traditional models of social evolution posit that initial social groups Selleckchem AZD2014 formed due either to a loss of dispersal (the subsocial

route) or active group formation (the parasocial route). These groups presumably functioned as aggregations, with all individuals producing and caring for their own offspring (Oster & Wilson, 1978). Asymmetries in these behaviors evolved as secondary kin-selected adaptations (Hamilton, 1964), which were then amplified as concentration of reproduction into one or a few individuals released constraints on morphological adaptation to more and more specialized subsets of tasks (West-Eberhard, 1989; Gadagkar, 1997). Thus, to arrive at eusociality from a solitary ancestor required multiple learn more successive evolutionary changes: first, a shift from solitary breeding to either loss of dispersal or group joining; second, a shift from independent to cooperative brood care; and third, a shift from equal reproductive

efforts to cessation of reproduction by some group members. Although this stepwise view follows a logical progression of social structures, the number of evolutionary transitions involved suggests that eusociality should be relatively difficult to evolve, as a multistep process would require adaptive benefits at every stage along the route, not just an adaptive end point. An alternative possibility that avoids this problem is that the evolution of eusociality may have occurred in a single evolutionary step: a shift in dispersal tendency or timing is accompanied by other eusocial traits as an automatic side effect (Michener, 1985; Linksvayer & Wade, 2005; Nowak et al., 2010).