Persistence: A model of lineage evolution based on the persistence strategy hypothesis

We propose a model of lineage evolution to follow the emergence of trade-offs between three strategies of persistence: economy, flexibility and robustness. The objective properties of the environment, such as temperature, salinity, illumination, are linked with the subjective experience of the organism that is exploring the environment, via probability functions expressing the likelihood of being exposed to each environmental signal. Organisms themselves are modeled according to Miller's theory of living systems, each represented with subsystems that process matter, energy, and information, such as boundaries (membranes), sensors, and internal transducers. The mechanisms of flexibility and robustness are expressed via the properties of these critical subsystems, many welldefined in Miller's theory. The energetic costs of manufacturing and maintaining the critical subsystems factor into the organism's strategy of economy and help define the tradeoffs between maximizing flexibility and robustness while minimizing their costs. These trade-offs are collectively depicted on a "persistence triangle, " which encompasses the entire landscape of trade-off solutions that lineages can explore during their evolution. We discuss trajectories of movement on the triangle, both for lineages in the course of their evolution (via emergence of new mechanisms of flexibility and robustness, and bifurcation into new lineages), as well as individual organisms during their lifetime (via learning, dormancy and life stages, such as egg, larva, and pupa). This model can serve as a recipe for creating a simulation that visualizes how organisms explore persistence strategy trade-offs during evolution.