Sijilmassi et al. offer a novel account of the role of fitness interdependence in motivating social cooperation. Questions remain, however, about what exactly perceived fitness interdependence entails and how it is generated in different coalitional settings. The present comment seeks to foreground those questions and suggest avenues for extending the authors' argument by bringing it into conversation with related research from political science and philosophy.

According to the authors, strategic agents design myths to promote a perception of fitness interdependence in potential coalition members. In large groups, this perception is a product of the extent to which “each individual benefits from the general welfare of other group members” (target article, sect. 3.2, para 3). This definition is ambiguous regarding whether the welfare in question refers to the aggregate group welfare or to the welfare of each individual member. Between groups with the same aggregate welfare, an individual who can anticipate being in the lower part of the socioeconomic distribution will likely have a higher perceived fitness interdependence with a group in which goods are distributed more equally or in which the welfare of the worst off is prioritized (Buchak, Reference Buchak2017; Fleurbaey, Reference Fleurbaey2010; Rawls, Reference Rawls1999).

Correspondingly, myths designed to elicit broad cooperation may offer signals not only about the longevity of the group but also about its internal organization, distributive characteristics, and associated quality of life. An illustration of this point comes from India, where as Prerna Singh shows, some elites have successfully mobilized subnational sentiment by appealing to “the idea of an equal, horizontal political community” that transcends caste and religious distinctions. On the other hand, where myths sought to entrench existing inequalities, they were more likely to inhibit the development of an inclusive subnational identity and its associated welfare benefits (Singh, Reference Singh2015, pp. 83, 94, 104–107, 182–183).

The authors further note that when members of a large coalition perceive they have a high degree of fitness interdependence, “they should be more willing to invest their limited resources for the sake of other group members” (target article, sect. 3.2, para 8). Underlying this statement is a claim about the importance of reciprocity, which can cement the perception of interdependence by rendering the reciprocator valuable to her partner (Barclay, Reference Barclay2020). Reciprocity involves a symmetrical relationship in which each party voluntarily responds to similar treatment by the other (Fehr & Gachter, Reference Fehr and Gächter1998; Kahan, Reference Kahan2003; Kolm, Reference Kolm2008). For reciprocal relations to be sustained over time, there should be a sense of balance, as well as trust that others will reliably act in kind (Becker, Reference Becker1986; Rothstein, Reference Rothstein, Banting and Kymlicka2017). In a large group, however, individuals may differ significantly in how they experience the costs of a given contribution (Brown, Reference Brown2020; Goodin, Reference Goodin2002). If the value of public goods is distributed evenly, then those whose participation is more costly may have a lower perceived interdependence than others because they have contributed more for roughly the same benefit (Ostrom, Reference Ostrom, Ostrom and Walker2003).

This problem may be resolved if all members feel that the benefits of cooperation are equivalent or proportional to its burdens (Brown, Reference Brown2020; Mau, Reference Mau2004). This condition is likely to be met when burdens imposed are roughly equal for all and when institutions treat everyone impartially (Freitag & Bühlmann, Reference Freitag and Bühlmann2009; Rothstein & Stolle, Reference Rothstein, Stolle, Hooghe and Stolle2003; Svallfors, Reference Svallfors2013). Thus, as Bo Rothstein has argued, the high level of cooperation in Nordic countries is a product not of culture or history but of an institutional design that sustains reciprocity by treating people evenhandedly (Rothstein, Reference Rothstein, Banting and Kymlicka2017).

In keeping with these observations, strategic agents might emphasize themes of trust and institutional universality in their myths to signal to members that they can rely on ongoing, fair reciprocal relations. For example, according to Rogers Smith, the story of American peoplehood invoked by Thomas Paine and the Declaration of Independence stressed political equality and the guarantee of individual rights to promote trust and convey the benefits of cooperation for all (Smith, Reference Smith2003b, p. 60). Narratives based on the idea of divine election and covenant also emphasize the entrusting of a people with a sacred mission, embodied in a law that all members must follow, and their reciprocal trust in one another to achieve that mission (Smith, Reference Smith2003a, pp. 49–58).

Finally, the authors state that identity fusion, including the feeling of “intense kin-like bonds,” is a valuable proximate measure for perceived fitness interdependence because it captures “the extent to which individuals perceive their fate to be inseparable” (target article, sect. 3.2, para 3) from that of others. While identity fusion may help to solve coordination problems by aligning individual behavior with the needs of the group, scholars acknowledge that it can also be invoked in ways that are detrimental to fitness (Cronk & Atkipis, Reference Cronk and Atkipis2018). A recent body of research on political polarization has highlighted the divisive implications of group identity, which can undermine generalized trust and cooperation (Bonomi, Gennaioli, & Tabellini, Reference Bonomi, Gennaioli and Tabellini2021; Mason, Reference Mason2015; Shayo, Reference Shayo2009; Tajfel & Turner, Reference Tajfel, Turner, Austin and Worchel1979). Groups with high political identity fusion may demonstrate “tribal corruption effect,” in which they protect the in-group's reputation by suppressing rather than punishing bad behavior within it (Jost, Baldassarri, & Druckman, Reference Jost, Baldassarri and Druckman2022). Group identity has also been found to decrease the likelihood of social-welfare enhancing behavior toward out-group members (Chen & Xin Li, Reference Chen and Xin Li2009).

As a result, where identity fusion is activated on the sub-coalitional level, it could undermine percevied fitness interdependence with the larger group. To avoid such outcomes, strategic agents might choose to design myths that stress equal status and reduce esteem-seeking distinctions among members. For example, according to George Mosse, the creation of shrines to unknown soldiers in the aftermath of World War I set out to evade distinctions of rank and project an ideal of brotherhood and equal sacrifice. In the case of Germany in particular, he argues, such wartime myths aimed to strengthen nationalism following the country's defeat, and promote unity against the threat of class struggle and political division (Mosse, Reference Mosse1990). While this example also underscores the dangers of group identity, it indicates another way in which myths may seek to highlight internal features of the group as well as its longevity.