Richerson et al. have identified five conditions for cultural group selection (CGS) to be considered as a viable possibility to explain cultural variation across groups and societies. One such condition is intergroup competition: “while modern nations and the subgroups … differ in many ways from ancestral tribes, they rest on the innate foundations that evolved from competition between ethnolinguistic units” (sect. 2, para. 2), and “the success and failure of groups in such competitions is often determined by institutional and other cultural differences” (sect. 7, para. 1). The authors reason that intergroup competition for scarce resources such as cattle and territory, market share, or religious supporters motivates within-group cooperation, and creates cultural practices and culture-specific institutions. Intergroup competition allows some tribes, firms, or religions to survive and prosper, while others are marginalized. Ultimately, cultural norms and institutions are thought to provide selection pressures for genetic adaptations for social behavior, including parochial altruism.

Here we question the importance of intergroup competition in CGS and culture-led genetic evolution of adaptations for pro-social behavior. First, we take issue with the tendency in evolutionary theory in general, and in CGS in particular, to conceptualize intergroup competition as a one-dimensional and zero-sum game. Similar to inter-individual interactions (Deutsch Reference Deutsch1973; Schelling Reference Schelling1960), intergroup competition can vary in the degree of corresponding versus non-corresponding interests (Bornstein Reference Bornstein2003). In fact, CGS relies on variable-sum Prisoner's Dilemma game and Ultimatum Bargaining games when testing (parts of) CGS theory (Bowles & Gintis Reference Bowles and Gintis2011; Hagen & Hammerstein Reference Hagen and Hammerstein2006; Henrich Reference Henrich2004). Furthermore, intergroup competition often is multi-dimensional so that losses on one issue can be, and often are, offset by gains on another issue (Aaldering & De Dreu Reference Aaldering and De Dreu2012; De Dreu & Carnevale Reference De Dreu, Carnevale and Zanna2003). Accordingly, there are many alternative solutions to intergroup competition than “winner-takes-all,” including leaving the scene (withdrawal from the battlefield, entering a different market), or negotiating a settlement (De Dreu Reference De Dreu, Fiske, Gilbert and Lindzey2010; Pruitt & Rubin Reference Pruitt and Rubin1986). Indeed, tribes and small-scale societies not only raid but also trade (Horan et al. Reference Horan, Bulte and Shoran2005), firms merge much more often through negotiated deals than through hostile take-overs (Martynova & Renneboog Reference Martynova and Renneboog2008), and disputes between countries may involve some hostilities and barbed-wired fences, but rarely lead to warfare (Jones et al. Reference Jones, Bremer and Singer1996). Thus, intergroup interactions often involve some corresponding interests and can and are settled peacefully through negotiated deals that allow both sides, and their respective cultures, to survive and prosper. As such, it is difficult to see whether and how intergroup competition is, or has been, a powerful selective pressure on the evolution of group culture, and hence, culture-led genetic evolution.

Second, Richerson et al. suggest that this intergroup competition and CGS could explain cultural and genetic adaptations for parochial cooperation. While it is unclear exactly what types of adaptations can be hypothesized to exist via culture-led gene-culture coevolution, research on the proximate mechanisms underlying group cooperation does not seem to contain the footprint of intergroup competition as a strong selection pressure shaping group cooperation. Social psychology has discovered that parochial altruism can be motivated by both in-group love and out-group hate (Brewer Reference Brewer1999; Greenwald & Pettigrew Reference Greenwald and Pettigrew2014). In-group love refers to the tendency to sacrifice immediate self-interest to benefit the in-group and its members; out-group hate refers to the tendency to sacrifice immediate self-interest to harm, derogate, and aggress competing out-groups and their members (Allport Reference Allport1954; Brewer Reference Brewer1999; De Dreu et al. Reference De Dreu, Balliet, Halevy and Elliot2014). In-group love and out-group hate are conceptually and empirically distinct – in intergroup competition, humans may be motivated by in-group love, by out-group hate, or by some combination of both (De Dreu et al. Reference De Dreu, Balliet, Halevy and Elliot2014). Absent intergroup competition, or even the presence of other groups, humans may still be motivated by in-group love but, obviously, not by out-group hate. Intergroup competition is but one of the many drivers of in-group love.

Moreover, a meta-analysis of studies using cooperation games in psychology, economics, and sociology revealed robust intergroup discrimination in cooperation being due to in-group love rather than out-group hate (Balliet et al. Reference Balliet, Wu and De Dreu2014). Rivaling out-groups were treated the same way as unfamiliar strangers, suggesting that for cooperation it matters whether someone belongs to one's own group or not. Indeed, intergroup competition strengthens in-group love rather than out-group hate (Halevy et al. Reference Halevy, Bornstein and Sagiv2008; Reference Halevy, Weisel and Bornstein2012), both among adults (De Dreu et al. Reference De Dreu, Balliet, Halevy and Elliot2014; Halevy et al. Reference Halevy, Bornstein and Sagiv2008) and young children (Buttelmann & Böhm Reference Buttelmann and Böhm2014). In fact, oxytocin, an evolutionary ancient neuropeptide pivotal in social bonding, modulates in-group love rather than out-group hate (De Dreu et al. Reference De Dreu, Greer, Handgraaf, Shalvi, Van Kleef, Baas, Ten Velden, Van Dijk and Feith2010; Reference De Dreu, Greer, Van Kleef, Shalvi and Handgraaf2011; Shalvi & De Dreu Reference Shalvi and De Dreu2014). Thus, in-group love can emerge both in the presence and absence of intergroup competition, and intergroup competition motivates in-group love more than out-group hate. Accordingly, there is substantial room for negotiated settlements and peaceful coexistence of (culturally) different groups and societies, especially when between group interactions are multi-dimensional and variable-sum.

Third and finally, intergroup competition may not be necessary to explain the (genetic) evolution of psychological adaptations supporting (parochial) cooperation. For example, group membership can be a cue that another person is part of an individual's social network and people may cooperate with in-group members to increase their reputation to gain indirect benefits from others and avoid being excluded from the group. Intergroup competition, or even intergroup comparisons, are not needed to bring about these processes (see Balliet et al. Reference Balliet, Wu and De Dreu2014; Yamagishi et al. Reference Yamagishi, Jin and Kiyonari1999). Accordingly, a more parsimonious and empirically more valid perspective may be that cultural group selection is the outcome of individuals and their groups seeking to survive and prosper, and who, therefore, create norms and cultural practices that sustain and promote biologically prepared tendencies for in-group love. Some groups properly adapt to a changing environment (the entrance of competing out-groups included), and others are less able to adapt to changes in the environment (crop failures and earthquakes included). Whether exogenous pressures are social or non-social in nature, groups that organize and sustain in-group love survive, prosper, and spread, and with them their culture. In short, in-group love, not intergroup competition, is driving cultural group selection.