Evolutionary Transitions in Individuality and Life Cycle Closure

We propose a novel account of evolutionary transitions in individuality as life cycle closure: that is, the emergence of a new embedding life cycle. To characterize this process, we show how the life trajectory of lower-level entities (e.g., cells) can be coarse-grained into classes of a higher-level entity. We argue that only higher-level entities displaying two necessary conditions for the existence of a life cycle (e.g., multicellular organisms) have achieved life cycle closure. Throughout, we illustrate our point with stage-structured demographic models that yield a rigorous characterization of the conditions for life cycle closure.