Lemoine, S. R. T., Samuni, L., Crockford, C., & Wittig, R. M. (2022). Parochial cooperation in wild chimpanzees: A model to explain the evolution of parochial altruism. In Philosophical Transactions of the Royal Society B: Biological Sciences (Vol. 377, Issue 1851). Royal Society Publishing. https://doi.org/10.1098/rstb.2021.0149

This is an exceptional paper. The authors define “parochial altruism” as taking individual costs to benefit the in-group and harm the out-group, and propose a model for the evolution of parochial altruism. The model applies to chimpanzees, but the idea is that this model might perhaps also explain how parochial altruism evolved in humans.

For this purpose, the authors review a vast number of papers in the field of cooperation and aggression in wild chimpanzees (and, to some extent, other animals) .

The model they propose is a complex one. It is relevant, for the issues we talk about in this blog, that the authors propose a positive feedback loop between aggressive encounters with external groups, on the one hand, and collaboration and cohesion within the group, on the other.

For example:

• “In-group solidarity tends to increase in response to out-group conflict, suggesting a causal link between out-group threat and in-group cohesion” (p. 2).
• “Evidence across taxa, including birds and mammals, demonstrate an immediate increase of in-group cohesion and affiliation following out-group threat, pointing towards the link between out-group conflicts and in-group favoritism” (p. 2).
• “Cooperation is key in maximizing the chances of beneficial outcomes of out-group conflicts” (p. 5).
• Group conflicts favor “the emergence and maintenance of cooperation among non-related individuals, the maintenance of strong social ties, in-group favoritism and hostility towards out-group members” (p. 7).
• “The highly structured and collective border patrols and large coalitionary attacks observed in chimpanzees indeed suggest strong links between group-level cooperation and out-group threat” (p. 8).

All this is important and relevant for the origin of the state, as explained by my mentor, Juan Samaja. Individuals compete against each other (internal war), but the pressure of the external threats makes them unite against the common enemy (external war); this threat is one of the keys to the birth of the state, as already explained in Plato’s Republic.

Another interesting aspect is that the paper establishes a link between reciprocity and what we call “community”. “The accumulation of bonded relationships, embedded within a social network, provides a path by which group-level cooperation occurs. The hypothesis that direct reciprocity constitutes a mechanism enabling solving collective problems finds support in chimpanzees where regular social interactions within a community cement a sense of common belonging (a common affect), enabling group-level collective action and avoidance of defection” (p. 8). This of course works only for local groups and small-scale cooperation; large scale cooperation requires other normative and symbolic frameworks (a flag, a national narrative, etc.)

For those of you (readers) who follow my musings in this blog about the epistemological impact of social coordination, it is interesting to note that chimpanzees engage in border patrols, where they move along the edges of their territories to monitor and defend their boundaries. They check for signs of intruders, such as the scent of unfamiliar individuals or the sound of other chimpanzee groups in the area. If they detect signs of intrusion, they often engage in displays of aggression, such as vocalizing loudly, throwing rocks and branches, or charging at the perceived threat. Now, this behavior might be the oldest precursor of the cultural institution of “boundary”. This institution, incidentally, is the one that philosopher John Searle uses as an example to explain the very notion of “institutions” (differentiating a wall that encircles a village as a physical barrier that can’t be crossed from a symbolic stone that marks the limit of a village and shouldn’t be crossed). Once we humans learned how to play the game of boundaries on an institutional level, we started to demarcate boundaries on the epistemological level. Ancient Rhetoric is born as an exercise to argue for the property of land, to have the limits of one’s property recognized. In Plato’s Republic, the limits of the city are delineated hand in hand with the limits of the citizen (both are defined almost in the same way), as well as the boundaries of the concept (of the Good, for example). Even Kant’s transcendental deduction follows to the detail the format of a legal deductio aimed at demarcating the territory and the boundaries of a state (Kant applies this format to demarcate the limits… of pure reason).