Collective Movement and the Evolution of Cooperation

Presented by
Jaideep Joshi
Indian Institute Of Science, Bangalore
Jaideep Joshi, Vishwesha Guttal


Understanding the evolution of altruism is a fundamental question in biology.

Typically, a single group of altruists can be readily invaded by cheaters,

making the evolution and maintenance of altruism extremely difficult.

However, many social organisms form multiple dynamic groups with a high degree of merging

and splitting. In this talk, we ask the question, can altruism evolve and be

sustained in such grouping organisms?


We built an individual based model capable of displaying a wide range of

movement types including solitary movement, swarming groups,

large polarized groups, and groups with merge-split dynamics.

We assigned two kinds of behaviours to each individual, namely local flocking

interactions and cooperation-defection behaviour, and let both of them evolve.

We also derived analytically, the conditions required for altruism to be

maintained in such a population.


For low costs of cooperation, we find that the frequency of altruists is

substantially larger in the presence of local flocking interactions than in

the case of solitary movement. As cost increases the frequency of

altruists decreases. Analytically, we find that altruism can evolve only

when the group sizes satisfy a certain criteria.


Our study shows that even in the absence of kin-selection or limited dispersal,altruism can not only co-evolve with collective movement, but is also resistant to invasion by cheaters. Since group size distributions necessary for evolution of altruism may occur only in some highly specific niches, it is crucial to understand and conservethem.