Abstract
During an evolutionary transition in individuality (ETI), lower-level entities interact in such a way that they produce higher-level entities that become new units invoked in evolutionary explanation at this higher level (Michod, 2005; Okasha, 2006). In this paper, we will argue that to understand an ETI, it is crucial to first understand the type of ecological conditions under which the formation of higher-level entities can occur. For instance, from the perspective of a cell or, more abstractly, a particle, one will ask under what environmental conditions is it advantageous to become part of and possibly fully dependent on a larger entity such as a multicellular organism or, more abstractly, a collective? This leads to a view of ETIs in which being part of a larger entity is regarded as a potential strategy or phenotype from the point of view of the lower level. Starting from recent works in experimental and theoretical evolution (e.g., Black et al., 2020; Hammerschmidt et al., 2014, Bourrat et al., 2021), we will provide boundary conditions on the environment for ETIs to be possible. First, we will argue that the environment must be complex, where complexity is defined by the number of discrete states and an associated probability distribution, which can be connected to the notion of entropy in information theory. Second, we will argue that these states must have a sequential order that can be defined either spatially or temporally. Finally, we will argue that the difference between sequential states must be relatively smooth because large differences between sequential states would exceed the adaptive capacity of the entities undergoing the transition.
