The free energy requirements of biological organisms; implications for evolution

Abstract

Recent advances in nonequilibrium statistical physics have provided unprecedented insight into the thermodynamics of dynamic processes. The author recently used these advances to extend Landauer's semi-formal reasoning concerning the thermodynamics of bit erasure, to derive the minimal free energy required to implement an arbitrary computation. Here, I extend this analysis, deriving the minimal free energy required by an organism to run a given (stochastic) map $\pi$ from its sensor inputs to its actuator outputs. I use this result to calculate the input-output map $\pi$ of an organism that optimally trades off the free energy needed to run $\pi$ with the phenotypic fitness that results from implementing $\pi$. I end with a general discussion of the limits imposed on the rate of the terrestrial biosphere's information processing by the flux of sunlight on the Earth.