Ohad Lewin-Epstein - Can microbes solve the prisoner’s dilemma?

The evolution of cooperative behavior, which is costly to the donor but beneficial for the recipient, is among the most intriguing questions in evolutionary biology. As presented in the prisoners’ dilemma, cooperation is in many cases advantageous for the group, but disadvantageous for each of the individuals. Thus, according to natural selection we expect cooperative behavior to be eliminated. Yet cooperation is prevalent in nature. Several theories have been proposed to explain this phenomenon, including kin selection, proposing that natural selection can favor cooperation between kin, reciprocity, which suggests that repeating interactions or individual recognition can favor cooperative behavior, and others. But almost all theories share a common prominent attribute: they focus on the individuals’ genes, that is, they consider cooperation as a behavioral trait which is inherited only from parent to offspring. We suggest extending the perspective and consider elements that affect the individual’s tendency to cooperate, and can be transmitted both vertically (inherited from parent to offspring) and horizontally (between interacting individuals). One such element is the microbiome - the microbial community residing within a host. Microbes inhabit all multicellular organisms, and numerous studies demonstrated that the microbiome has a tremendous effect on its host health, development and behavior. We propose that natural selection on the microbes may favor those that induce their host to cooperate, and that this may help explain the evolution of cooperation in a wide range of organisms. Using mathematical analysis and computational simulations, we show that microbe-induced cooperation can evolve under a wide range of conditions.