How Can Metabolism Lead to Groups?

Abstract

Group formation is an often neglected first step in the evolution of cooperation. Group living can favor kin selection, reciprocity, group selection, or all three. How can metabolism lead to groups? Microbes frequently engage in syntrophy or “feeding together,” in which the waste of one microbe can become the substrate of another. Syntrophy can be viewed as a form of reciprocity, and the stoichiometry of these relationships can mediate evolutionary conflicts. Introducing chemiosmosis into syntrophic relationships adds a layer of complexity that is likely absent from purely fermentative interactions. Because of quantum electron transfer and supercomplex formation, purely chemiosmotic reactions proceed at higher rates than purely fermentative ones. The costs of end-product inhibition and the benefits of symbiotic partners that serve as sinks for excess products are both greater for chemiosmotic cells or organisms than for fermentative ones. Chemiosmosis can thus drive group formation. In this way, metabolism may lead to groups, groups may lead to cooperation, and cooperation may lead to complexity.

One of the most studied and most poorly understood concerns of ethology is why animals live in groups. Living in groups has been claimed to aid in the rearing of young, to facilitate mating, to increase foraging success, to reduce the risk of predation, to provide protection from inclement weather, and to increase swimming efficiency.

Daniel Rubenstein [1]