Natural Selection and Scale Invariance

Abstract

This review points out that three of the essential features of natural selection-competition for a finite resource, variation, and transmission of memory-occur in an extremely simple, thermalized molecular population, one of colliding "billiard balls" subject to an anisotropy, a directional flux of energetic molecules. The emergence of scaling behavior, scale invariance, in such systems is considered in the context of the emergence of complexity driven by Gibbs free energy, the origins of life, and known chemistries in planetary and astrophysical conditions. It is suggested that the thermodynamic formalism of statistical multifractality offers a parallel between the microscopic and macroscopic views of non-equilibrium systems and their evolution, different from, empirically determinable, and therefore complementing traditional definitions of entropy and its production in living systems. Further, the approach supports the existence of a bridge between microscopic and macroscopic scales, the missing mesoscopic scale. It is argued that natural selection consequently operates on all scales-whether or not life results will depend on both the initial and the evolving boundary conditions. That life alters the boundary conditions ensures nonlinearity and scale invariance. Evolution by natural selection will have taken place in Earth's fluid envelope; both air and water display scale invariance and are far from chemical equilibrium, a complex condition driven by the Gibbs free energy arising from the entropy difference between the incoming solar beam and the outgoing infrared radiation to the cold sink of space acting on the initial conditions within evolving boundary conditions. Symmetry breaking's role in the atmospheric state is discussed, particularly in regard to aerosol fission in the context of airborne bacteria and viruses in both current and prebiotic times. Over 4.4 billion years, the factors operating to support natural selection will have evolved along with the entire system from relative simplicity to the current complexity.

Keywords: Gibbs free energy; molecular dynamics; non-equilibrium thermodynamics; statistical multifractals; symmetry breaking.

Figure 1

(a) Solar flux at the top of the current atmosphere. Red curve for clear skies, blue curve for cloudy skies. The various spectral features are labelled by the molecules responsible. (b) Absorbed infrared radiation for the current atmosphere, with the absorption features labelled by the three main absorbers, H₂O, CO₂, and O₃. There are absorptions from N₂O, CH₄, and halocarbon molecules in the so-called window region between 7 and 14 microns. After Kiehl and Trenberth [39]. © American Meteorological Society. Used with permission.

Figure 1

(a) Solar flux at the top of the current atmosphere. Red curve for clear skies, blue curve for cloudy skies. The various spectral features are labelled by the molecules responsible. (b) Absorbed infrared radiation for the current atmosphere, with the absorption features labelled by the three main absorbers, H₂O, CO₂, and O₃. There are absorptions from N₂O, CH₄, and halocarbon molecules in the so-called window region between 7 and 14 microns. After Kiehl and Trenberth [39]. © American Meteorological Society. Used with permission.

Figure 2

The entropy of a radiative source is Q/T where Q is the energy and T the absolute temperature. The emitting temperature of the sun is about 5800 K, and that of the Earth is about 255 K. Photosynthesis by the entire biosphere is approximately 1% of the solar flux. The units on the figures are Wm⁻². Note that the currently accepted value for the average influx is 1361 Wm⁻².

Figure 3

The phase diagram for water shows that the atmosphere can sample all three phases around the triple point, a property unique to water. Ice floats because water has its maximum density at 4C, or 277 K. Water vapor plays a crucial role in establishing atmospheric temperature via the interaction of its phase changes and spectroscopic properties which establish the thermodynamics of the planet. After Vaida and Tuck [40].