We study the influence that resource availability has on cooperation in the context of hunter-gatherer
societies. This paper proposes a model based on archaeological and ethnographic research on resource
stress episodes, which exposes three different cooperative regimes according to the relationship
between resource availability in the environment and population size. The most interesting regime
represents moderate survival stress in which individuals coordinate in an evolutionary way to increase
the probabilities of survival and reduce the risk of failing to meet the minimum needs for survival.
Populations self-organise in an indirect reciprocity system in which the norm that emerges is to share
the part of the resource that is not strictly necessary for survival, thereby collectively lowering the
chances of starving. Our findings shed further light on the emergence and evolution of cooperation in
hunter-gatherer societies.
