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Déterminants évolutionnistes de la socialité
Collective interactions are recurrent in microbes, though paradoxical with respect to natural selection : individual traits that support sociality are costly, hence prone to exploitation by noncarriers. Among the many related theoretical models, most overlook the physical process of group formation, relying on static and idealized formulations.
In a first part, I design a general formal framework describing the evolutionary dynamics of a social trait that enhances individual propensity to interact as well as aggregates cohesion. I show that, under some conditions on the group size distributions experienced by the social and asocial types, socials may get positively assorted with no recognition ability, but merely as a mechanical consequence of them being more aggregation-prone, suggesting a weaker requirement (differential attachment) for their success than usually assumed (preferential attachment).
In a second part, I substantiate this proof of principle implementing a biologically relevant computational model for aggregation, where individuals exert interaction forces on each other whose intensities depend on their type. I show that the emergence and maintenance of sociality is compatible with such group formation processes, and specify under which conditions on the microscopic parameters of motion and ecological parameters.
This work suggests a parsimonious, elementary scenario for the evolution of sociality in groups of arbitrary sizes bereft of high-level cognitive abilities and interaction with kins. It might shed light both on the evolutionary determinants of social structure in species such as dictyostelids and myxobacteria, and on the possible origins of multicellularity.