A Thermodynamic Perspective on Natural Selection

A novel thermodynamic perspective on natural selection is presented. In the case that life continuity is optimized in an ideal system, where relatively constant and homogeneous selective pressures favour a given competing species, natural selection leads that system to a stationary state of maximum genotypic uniformity of life and maximum sustainable consumption of available energy by life (competitive equilibrium). Structurally and functionally, this optimizing tendency towards competitive equilibrium looks similar to the optimizing tendency towards thermodynamic equilibrium of classical thermodynamics (maximum energetic uniformity and maximum degradation of available energy). The principle of competitive exclusion may thus be conceptually viewed as an ecological manifestation of the second law of (classical) thermodynamics. On the other hand, the novel thermodynamic perspective on natural selection is discussed with regard to the open and nonequilibrium system of nature, where selective pressures vary in space and time. In this case, natural selection can induce diversity instead of uniformity, though an optimizing tendendcy towards maximum sustainable consumption of resources (optimization of life continuity) always remains. Overall, it is concluded that the action of natural selection favours the maximization of the sustainable consumption of energy at the level of individual organism.     

Teleosemantics Without Natural Selection

Ruth Millikan and others advocate theories which attempt to naturalize wide mental content (e.g. beliefs’ truth conditions) in terms of function in the teleological sense, where a function is constituted in part by facts concerning past natural selection involving ancestors of a current entity. I argue that it is a mistake to base content on selection. Content should instead be based on functions which though historical, do not involve selection. I sketch an account of such functions.     

A Simulation Study of Truncation Selection for a Quantitative Trait Opposed by Natural Selection

A quantitative character controlled at one locus with two alleles was submitted to artificial (mass) selection and to three modes of opposing natural selection (directional selection, overdominance and underdominance) in a large random-mating population. The selection response and the limits of the selective process were studied by deterministic simulation. The lifetime of the process was generally between 20 and 100 generations and did not appear to depend on the mode of natural selection. However, depending on the values of the parameters (initial gene frequency, selection intensity, ratio of the effect of the gene to the environmental standard deviation, fitness values) the following outcomes of selection were observed: fixation of the allele favored by artificial selection, stable nontrivial equilibrium, unstable equilibrium and loss of the allele favored by artificial selection. Finally, the results of the simulation were compared to the results of selection experiments.     

Natural Selection and Y-Linked Polymorphism

Several population genetic models allowing natural selection to act on Y-linked polymorphism are examined. The first incorporates pleiotropic effects of a Y-linked locus, such that viability, segregation distortion, fecundity and sexual selection can all be determined by one locus. It is shown that no set of selection parameters can maintain a stable Y-linked polymorphism. Interaction with the X chromosome is allowed in the next model, with viabilities determined by both X- and Y-linked factors. This model allows four fixation equilibria, two equilibria with X polymorphism and a unique point with both X- and Y-linked polymorphism. Stability analysis shows that the complete polymorphism is never stable. When X- and Y-linked loci influence meiotic drive, it is possible to have all fixation equilibria simultaneously unstable, and yet there is no stable interior equilibrium. Only when viability and meiotic drive are jointly affected by both X- and Y-linked genes can a Y-linked polymorphism be maintained. Unusual dynamics, including stable limit cycles, are generated by this model. Numerical simulations show that only a very small portion of the parameter space admits Y polymorphism, a result that is relevant to the interpretation of levels of Y-DNA sequence variation in natural populations.     

Natural Selection and Material Culture

Natural selection is the basis of all evolutionary applications in biology as well as studies of cultural process in archaeology. Natural selection is important because it allows us the tools to talk not only about variation in biological systems but also material culture that are the by-products of the human decision-making processes. In this paper, we provide a baseline of the concept of natural selection and explanatory application in evolutionary archaeology.     

Adaptation and Natural Selection revisited

In Adaptation and Natural Selection, George C. Williams linked the distinction between group and individual adaptation with the distinction between group and individual selection. Williams’ Principle, as we will call it, says that adaptation at a level requires selection at that level. This is a necessary but not a sufficient condition; for example, group adaptation requires group selection, but the fact that group selection influences a trait’s evolution does not suffice for the resulting trait frequency to be a group adaptation. What more is required? In this paper, we describe an answer to this question that has been developed in multilevel selection theory. We also discuss an alternative framework for defining units of adaptation that violates Williams’ Principle.     

Natural Selection and Age-Structured Populations

This paper studies the properties of a new class of demographic parameters for age-structured populations and analyzes the effect of natural selection on these parameters. Two new demographic variables are introduced: the entropy of a population and the reproductive potential. The entropy of a population measures the variability of the contribution of the different age classes to the stationary population. The reproductive potential measures the mean of the contribution of the different age classes to the Malthusian parameter. The Malthusian parameter is precisely the difference between the entropy and the reproductive potential. The effect of these demographic variables on changes in gene frequency is discussed. The concept of entropy of a genotype is introduced and it is shown that in a random mating population in Hardy-Weinberg equilibrium and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the covariance in entropy and reproductive potential. This result is an information theoretic analog of Fisher''s fundamental theorem of natural selection.