As biologist Scott Gilbert and his colleagues write, “Almost all development may be codevelopment. By codevelopment we refer to the ability of the cells of one species to assist the normal construction of the body of another species.” This insight changes the unit of evolution. Some biologists have begun to speak of the “hologenome theory of evolution,” referring to the complex of organisms and their symbionts as an evolutionary unit: the “holobiont.” They find, for example, that associations between particular bacteria and fruit flies influence fruit fly mating choice, thus shaping the road to the development of a new species. To add the importance of development, Gilbert and his colleagues use the term “symbiopoiesis,” the codevelopment of the holobiont. The term contrasts their findings with an earlier focus on life as internally self-organizing systems, self-formed through “autopoiesis.” “More and more,” they write, “symbiosis appears to be the ‘rule,’ not the exception…. Nature may be selecting ‘relationships’ rather than individuals or genomes.” —Anna Lowenhaupt Tsing, The Mushroom at the End of the World: On the Possibility of Life in Capitalist Ruins













