Towards the integration of collective behaviour and social evolution

Collective behaviour is ubiquitous in nature. Defined as individual-level local interactions that give rise to emergent patterns at the group level, collective behaviour spans multiple biological levels, including molecules, cells, organisms and societies. Many collective behaviours are beneficial at the group level and observed even in species that form groups of low genetic relatedness. However, group-level benefits alone are often not sufficient to explain the evolution and maintenance of cooperative behaviours in well-mixed populations. Establishing such an understanding is the purview of social evolution; however, theoretical tools from social evolution have seldom been applied to the field of collective behaviour. Towards closing this research gap, I present a case study using multilevel selection theory to study the evolution of coordinated (aligned) collective behaviour under threat of predation. I derive analytical solutions, demonstrating that the group-level benefits of collective behaviour can lead to its evolution, even when the behaviour is initially costly at the individual level. To test the model's predictions, I suggest we will be able to tease apart the levels of selection using biohybrid experimental systems, which integrate virtual prey with real-life predators. In sum, I suggest (and then demonstrate) that the precise application of social evolution theory can provide testable hypotheses, towards unravelling how collective behaviours evolved. • Social evolution theory is applied to the evolution of collective behaviours. • Coordinated collective behaviour may evolve entirely through group-level benefits. • Biohybrid systems are proposed for empirical testing of the theory. • Social evolution and collective behaviour integration give new theoretical insights.