Theoretical Evolutionary Rates in Plant Groups and the Fossil Record

Abstract

An attempt is made to estimate a mathematical expression for the underlying mean rate of evolution in organic systems, and in particular those of various plant groupings. This was done by considering the thermodynamic constraints on any system tending towards greater levels of complexity with time (or showing a progressive decrease in randomness). Orderliness is here equated with genetic-information, and rates of evolution are expressed as rates of information-accumulation. Mathematical relationships for evolutionary rates may also be expressed in terms of species number changes. Scattering of evolutionary rates about a theoretical mean is shown to be, in part, the result of environmental factors influencing the fixation of mutations within a phyletic group; “plasticity” (or physiologic adaptability) of any given genome is hypothesized to be related to regulatory-gene expressions. The discription of a mean rate with phyletic group scattering attempts to reconcile “steady-state” and differential rate models for evolution. A literature study of species citations indicates a high and positive correlation between geologic map area (and volume) during various time periods and the appearance of species per unit time. These data suggest that various biasing factors, influencing the preservation and interpretation of fossil data, make the fossil record an unreliable tool with which to gauge flux in species number changes.