Energetics and evolutionary fitness

I pass on the first paragraph of a perspectives piece in PNAS by Vermeij et al. that gives their message more thoroughly than the paper's abstract. Motivated readers can obtain a copy of the whole essay from me. 

Organisms acquire energy and material resources and convert these to activity and living biomass (1). The role of energy as currency (or power, energy per unit time) in evolution has long been recognized (2–6), but how energy acquisition and allocation affect evolution remains the subject of disagreement. In this perspective, we show how different assumptions about whether life operates in a dynamic steady state or whether it has expanded over the course of its history lead to contrasting predictions about adaptation, natural selection, and “fitness.” We conclude that models based on steady-state assumptions do not adequately account for observed patterns of adaptive change and evolutionary trends of increasing power and species richness over long periods of time, whereas models based on individual and collective power, which incorporate activity and the effects of organisms on their surroundings as components of survival and reproduction, reflect the history of adaptation more faithfully. The issue is important because energy (the currency of life) and power (energy acquired and expended per unit time) offer a unified framework for interpreting the course and outcomes of evolution. Models based on assumptions that reflect observed patterns should be more predictive than zero-sum models not only in the realm of evolution but also in ecology and economics.