Sijilmassi et al. nicely summarize the evidence for the prevalence of group-myths regarding shared ancestry and histories, and raise the interesting question of why they are so common. They seem to suggest that such myths are prevalent because they trigger an evolved psychology attuned to histories of “fitness-interdependence.” In large-scale societies, where no real fitness interdependence exists, we take Sijilmassi et al. to be arguing that these cognitive mechanisms misfire because the narratives are crafted to act as compelling superstimuli. For instance, a Jew might help out another Jew because he is led to erroneously believe his own success depends on that of his co-religionists, or that he is liable to have repeated interactions with a co-religionist and therefore have the favor returned. However, since there are millions of Jewish people spread throughout the globe, neither of these are likely. Consequently, Jews who willingly help out other Jews, just because they share a purported ancestor or history must be acting on an erroneous belief that their shared ancestor was quite a bit more recent or their community orders of magnitude smaller.
We present an alternative explanation that does not require such an extreme “error.” Specifically, we suggest narratives around ancestry or recent history are one way, among many, to create or alter our common understanding of who belongs to the in-group and therefore is subject to specific rights and responsibilities. These beliefs are self-enforcing, even in the absence of actual, or inaccurately perceived, fitness-interdependence.
This explanation builds off the game-theoretic logic of how group-based norms are enforced and sustained in equilibria. In standard models of norm enforcement, agents are incentivized to abide by norms because others who witness the norm violation punish the norm violator, and those who fail to punish when expected to are themselves subject to similar social-costs (Boyd & Richerson, Reference Boyd and Richerson1992; Mathew, Reference Mathew2017). This recursive logic can sustain arbitrary norms in equilibrium, but often sustains norms that depend on group membership, such as requiring cooperation with co-religionists (Richerson et al., Reference Richerson, Baldini, Bell, Demps, Frost, Hillis and Zefferman2016). Importantly, which boundaries matter and who is considered a member of that group is itself part of the norm, and can be self-enforcing the same way norm compliance might be. For instance, if everyone else treats religion as the defining feature of group membership, and everyone considers you to be a member of our religion, I might be sanctioned for not cooperating with you, and so will find it in my interest to do so. Also, importantly, the grouping need not be based on anything “real”; it simply needs to promote a shared understanding of who is and isn't a member and therefore to whom the norms apply.
By this account, the historical myths described in the target article are attempts to define group membership or shift who is ingroup along these lines. So long as the narratives create a shared understanding of the boundary and of the associated norms for treating ingroup and outgroup members, they can be impactful, even if nobody presumes the narratives are accurate reflections of recent history or current interdependence.
Consistent with this account, groups coalesce around all sorts of factors – religious, national, occupational, or class-based interest groups, often overriding shared ancestry, history, or actual interdependence. Confronted with the international diversity of pilgrims in Mecca, Malcolm X, till then a Black nationalist, proclaimed Islam as “the one religion that erases from its society the race problem” (Malcolm & Haley, Reference Malcolm and Haley1990), highlighting how religion can override ancestry-based identities. Ethiopian Jews were granted citizenship and transit to Israel, illustrating that a lack of recent shared history can be easily overlooked, even in a non-proselytizing religion. Birth-right citizenship laws demonstrate that neither notions of shared ancestry nor history are necessary for state building. International workers movements mobilized working class people living across oceans. There is no real interdependence among the millions of strangers in each of these social categories – a worker might help out another worker out of “class solidarity” even if they have no chance of seeing each other again and even if her benevolent action isn't going to meaningfully impact the class system.
The fact that group boundaries are publicly broadcast and that membership is often construed as discrete is also consistent with our preferred explanation (Hoffman, Yoeli, Dalkiran, & Nowak, Reference Hoffman, Yoeli, Dalkiran and Nowak2020; Hoffman & Yoeli, Reference Hoffman and Yoeli2022). Because a shared understanding of group-boundaries is imperative, it is not surprising that mythologies tend to be propagated in highly public forums (e.g., public schools, citizenship ceremonies, or sports arenas), and reinforced with highly visible practices (e.g., anthem singing, ritualized praying, or wearing union membership buttons). Furthermore, the need for agreement about group membership can explain artificially discretized boundaries such as those created by one-drop laws (Jordan & Spickard, Reference Jordan and Spickard2014), all-or-none rules of religious and national membership, and corporate lineages that discretize genetic relatedness (Alvard, Reference Alvard2011). If interdependence were all that mattered it's not clear why artificial discretization would be necessary. Likewise, if designing a myth to be a superstimuli for interdependence-detecting cognition were all that mattered, one would not need to ensure group membership was so publicly visible; it would only matter that individuals be privately informed, or misinformed, about whose welfare they depend on.
Finally, myths about shared ancestry and history may nonetheless commonly define group boundaries because societies have developed in a patterned way. Early forms of political organization were likely kin-based lineages, and as societies expanded they tended to take over, or merge with, neighboring groups. This means that shared ancestry and histories would often co-vary, even if imperfectly, with geography, location, institutions, cultural beliefs, and social-networks. This underlying structure provides functional benefits (e.g., pre-existing organization, coordinated expectations, efficient information flow) to defining group boundaries along such lines (Moya, Reference Moya2023; Moya & Boyd, Reference Moya and Boyd2015). Historical myths may also provide a convenient shorthand for a set of norms governing ingroup interactions that are analogous to those for pre-existing ancestry-based social groups. However, we suspect that as larger-scale societies emerge and institutions evolve, narratives about ancestry and history become less frequent means of defining group boundaries.
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Sijilmassi et al. nicely summarize the evidence for the prevalence of group-myths regarding shared ancestry and histories, and raise the interesting question of why they are so common. They seem to suggest that such myths are prevalent because they trigger an evolved psychology attuned to histories of “fitness-interdependence.” In large-scale societies, where no real fitness interdependence exists, we take Sijilmassi et al. to be arguing that these cognitive mechanisms misfire because the narratives are crafted to act as compelling superstimuli. For instance, a Jew might help out another Jew because he is led to erroneously believe his own success depends on that of his co-religionists, or that he is liable to have repeated interactions with a co-religionist and therefore have the favor returned. However, since there are millions of Jewish people spread throughout the globe, neither of these are likely. Consequently, Jews who willingly help out other Jews, just because they share a purported ancestor or history must be acting on an erroneous belief that their shared ancestor was quite a bit more recent or their community orders of magnitude smaller.
We present an alternative explanation that does not require such an extreme “error.” Specifically, we suggest narratives around ancestry or recent history are one way, among many, to create or alter our common understanding of who belongs to the in-group and therefore is subject to specific rights and responsibilities. These beliefs are self-enforcing, even in the absence of actual, or inaccurately perceived, fitness-interdependence.
This explanation builds off the game-theoretic logic of how group-based norms are enforced and sustained in equilibria. In standard models of norm enforcement, agents are incentivized to abide by norms because others who witness the norm violation punish the norm violator, and those who fail to punish when expected to are themselves subject to similar social-costs (Boyd & Richerson, Reference Boyd and Richerson1992; Mathew, Reference Mathew2017). This recursive logic can sustain arbitrary norms in equilibrium, but often sustains norms that depend on group membership, such as requiring cooperation with co-religionists (Richerson et al., Reference Richerson, Baldini, Bell, Demps, Frost, Hillis and Zefferman2016). Importantly, which boundaries matter and who is considered a member of that group is itself part of the norm, and can be self-enforcing the same way norm compliance might be. For instance, if everyone else treats religion as the defining feature of group membership, and everyone considers you to be a member of our religion, I might be sanctioned for not cooperating with you, and so will find it in my interest to do so. Also, importantly, the grouping need not be based on anything “real”; it simply needs to promote a shared understanding of who is and isn't a member and therefore to whom the norms apply.
By this account, the historical myths described in the target article are attempts to define group membership or shift who is ingroup along these lines. So long as the narratives create a shared understanding of the boundary and of the associated norms for treating ingroup and outgroup members, they can be impactful, even if nobody presumes the narratives are accurate reflections of recent history or current interdependence.
Consistent with this account, groups coalesce around all sorts of factors – religious, national, occupational, or class-based interest groups, often overriding shared ancestry, history, or actual interdependence. Confronted with the international diversity of pilgrims in Mecca, Malcolm X, till then a Black nationalist, proclaimed Islam as “the one religion that erases from its society the race problem” (Malcolm & Haley, Reference Malcolm and Haley1990), highlighting how religion can override ancestry-based identities. Ethiopian Jews were granted citizenship and transit to Israel, illustrating that a lack of recent shared history can be easily overlooked, even in a non-proselytizing religion. Birth-right citizenship laws demonstrate that neither notions of shared ancestry nor history are necessary for state building. International workers movements mobilized working class people living across oceans. There is no real interdependence among the millions of strangers in each of these social categories – a worker might help out another worker out of “class solidarity” even if they have no chance of seeing each other again and even if her benevolent action isn't going to meaningfully impact the class system.
The fact that group boundaries are publicly broadcast and that membership is often construed as discrete is also consistent with our preferred explanation (Hoffman, Yoeli, Dalkiran, & Nowak, Reference Hoffman, Yoeli, Dalkiran and Nowak2020; Hoffman & Yoeli, Reference Hoffman and Yoeli2022). Because a shared understanding of group-boundaries is imperative, it is not surprising that mythologies tend to be propagated in highly public forums (e.g., public schools, citizenship ceremonies, or sports arenas), and reinforced with highly visible practices (e.g., anthem singing, ritualized praying, or wearing union membership buttons). Furthermore, the need for agreement about group membership can explain artificially discretized boundaries such as those created by one-drop laws (Jordan & Spickard, Reference Jordan and Spickard2014), all-or-none rules of religious and national membership, and corporate lineages that discretize genetic relatedness (Alvard, Reference Alvard2011). If interdependence were all that mattered it's not clear why artificial discretization would be necessary. Likewise, if designing a myth to be a superstimuli for interdependence-detecting cognition were all that mattered, one would not need to ensure group membership was so publicly visible; it would only matter that individuals be privately informed, or misinformed, about whose welfare they depend on.
Finally, myths about shared ancestry and history may nonetheless commonly define group boundaries because societies have developed in a patterned way. Early forms of political organization were likely kin-based lineages, and as societies expanded they tended to take over, or merge with, neighboring groups. This means that shared ancestry and histories would often co-vary, even if imperfectly, with geography, location, institutions, cultural beliefs, and social-networks. This underlying structure provides functional benefits (e.g., pre-existing organization, coordinated expectations, efficient information flow) to defining group boundaries along such lines (Moya, Reference Moya2023; Moya & Boyd, Reference Moya and Boyd2015). Historical myths may also provide a convenient shorthand for a set of norms governing ingroup interactions that are analogous to those for pre-existing ancestry-based social groups. However, we suspect that as larger-scale societies emerge and institutions evolve, narratives about ancestry and history become less frequent means of defining group boundaries.
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