Abstract
Evolutionary transitions in individuality (ETIs) are often conceptualized in a static rather than dynamical way. Abstractly, once an ETI is complete, the particles or lower-level entities (e.g., genes or cells) are regarded as the “bricks” constituting the “building” of the higher-level entities or collective (e.g., chromosomes or multicellular organisms). However, this static view underplays the dynamical nature of the collective—results of interactions between lower-level entities are only described in a phenomenological way. This is particularly detrimental when studying ETIs. We propose a different view in which both particles and collectives have their own developmental (internal) and ecological dynamics (external). One subtlety of this view is that the dynamics at both levels are intertwined in nested systems: a process described as the ecology of the cells is the development of the multicellular organism. Likewise, the development of the cells constrains their ecology and, ultimately, limits the space that can be explored by collectives. In this paper, we will focus on how regarding nested systems from the point of view of their life cycle, as a central object for the study of ETIs, can help clarify the problem of nested dynamics. First, we will show under what conditions a dynamical system can qualify as a life cycle by drawing from the Darwinian properties framework and, in particular, Godfrey-Smith’s (2009) Darwinian space. Second, we will show how focusing on life cycle rather than the entity at one point of the life cycle permits us to clarify the problems of entangled timescales and fuzzy boundaries, particularly in the context of the ecological scaffolding scenario of ETIs (Black et al., 2020; Doulcier et al., 2020). Third, we will contrast this view with some alternative formalizations of the ETIs. Finally, we will outline a research program detailing how this focus could be used to tackle outstanding questions in the field.
