Black Queen markets: commensalism, dependency, and the evolution of cooperative specialization in human society

Where positive externalities are structural inevitabilities of particular behaviors and strategies (e.g. “Black Queen (BQ) functions”), stable commensalism is both possible and likely even between individuals who would otherwise be in close competition, and the coexistence thus stabilized generates opportunity for the eventual development of mutual and collective benefit. Here we review examples of BQ functions in animal behavior, both in the natural world and in human economies, with a focus on how these functions encourage the evolution of specialization and division of labor. The non-human examples we consider range from microbial systems to vertebrate communities while the human examples consider economic agents ranging from foraging societies to superpowers. With these examples, we discuss four classes of BQ functions: (i) functions that protect against harmful things in the environment; (ii) functions that provide products with value added relative to their constituent parts; (iii) functions that provide structures that can be utilized by other organisms; and (iv) functions that yield information. We also explore a set of examples where BQ-stabilized commensal relationships developed into two-way exchange relationships in human systems: (i) the ancient mutualism between humans and dogs, (ii) the division of labor in human societies between sexes and age groups, and (iii) the dominance of Silicon Valley over other regional technology centers. We conclude that BQ functions are an underappreciated motivator of markets and communities and suggest future experimental evolution research encouraged by our perspective.