Using simulation and analytical theory borrowed from statistical mechanics, we
find that simple community structure can be surprisingly effective at maintaining
cooperation, despite a relatively large influx of heritable cheating (by any
mechanism, such as mutation, transformation, or migration). When this influx
exceeds a marked threshold, however, cooperation is lost. Our findings are of
general interest across a wide range of biological and social sciences, and our
framework may provide a parsimonious model of somatic evolutionary processes
leading up to the transition from normal to cancerous tissue.

A large body of previous work has focused on the evolution of cooperation rather
than its maintenance and, while superficially similar, these two problems require
very different approaches. In a population of defectors, the appearance of a
cooperator would be quite a novel – even anomalous – innovation, and previous
work has therefore asked whether a single cooperating mutant introduced into a
population of defectors is likely to reach fixation. In a population of cooperators,
however, defectors (or “cheaters”) can arise by loss‐of‐function mutations (or
transformations) and can therefore appear quite frequently. It is thus more
accurate to model the appearance of cheaters in a population of cooperators as
recurring throughout the population at some rate of influx. As a result, the
problem of cooperation maintenance is quite different than problems previously
addressed, and yet its relevance to biology and the social sciences is self‐evident.

In review.

Background:

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