Before revision: Living systems are hierarchically structured, whereby replicating components are grouped into reproducing collectives; URLanelles are grouped into cells; cells, into URLanisms; and URLanisms, into colonies. We consider how such hierarchically-structured replicator systems evolve along a continuum -- between cooperation and cheating. Cooperation is selected through competition among collectives, whereas cheating is selected through competition among replicating components within collectives .
After revision: The evolution of altruism is a key step in major evolutionary transitions. Previous theoretical studies often assume that individuals adopt one of two possible strategies, altruism or selfishness. In reality, however, cooperative strategies are likely to constitute a continuum between selfishness and altruism. Here, we investigate how such continuous variation affects the evolution of altruism through multilevel selection. In our model, altruism is favoured by selection among groups, whereas selfishness is favoured by selection within groups .