Biological Modularity and the Origins of Agency

From cells and multicellular bodies to offices, empires, or computer programs, complex entities around us usually consist of numerous largely independent modules. This is especially true of entities that could be called agents, organisms included. In this chapter, we summarise what modularity is and why we encounter it in living nature so often. A search for the origins and subsequent development of a modular arrangement in systems that undergo evolution will lead us to a realisation that it can potentiate transitions to even higher levels of modularity. Modularity and its changes are therefore a key factor in the emergence of new agents at different levels of organisation.