ADDING POWER TO MACROEVOLUTIONARY THEORY

Macroevolution can be characterized by three interrelated goals: (1) Documenting the history of life, including the succession of taxa in time and space, their changes in form and function, and major events such as key innovations, the Cambrian explosion, and mass extinctions. (2) Characterization of the processes responsible. (3) The search for generalities, rules or laws, that might help explain this history given the processes at work. While the first two components are quite mature, finding generalities has been more difficult. However, viewing macro-evolution through the lens of power, the rate at which organisms perform work, Geerat Vermeij (2019) argues that “the history of life ... exhibits an emergent directionality towards increasing power at large ecosystem-wide scales”. More specifically he argues that there has been “an increase in collective power, an expansion of the living world away from thermodynamic equilibrium, driven by the cumulative effects of selective competition for locally scarce resources.” Given his incisive arguments my goals are: (1) To show that the central role of power is implicit in Darwin’s theory of evolution. (2) To emphasize that the casting of macroevolutionary change in terms of the acquisition and use of power has a unifying effect, in part because it requires an explicit account of how organisms interact with their environment. This is important because our macroevolutionary tradition often focuses on the evolutionary dynamics of (typically a subset) of the players, specific clades, without a framing that automatically includes the environment. (3) Provide a simple quantitative scheme for thinking about how power both evolves and is constrained. (4) Highlight the parallels between the macroevolutionary analysis of the acquisition and use of power with ecological thermodynamics, especially ecological succession. A core component of the eco-thermodynamic approach is the importance of information and control in ecosystem function, ideas that are largely absent from macroevolution. An open question is the extent to which ecological succession recapitulates the evolution of power. Finally, I note that the eco-thermodynamic considerations help elucidate why it is hard to draw decisive conclusions from clade-based macroevolutionary analysis.