Evolution in a nutshell

an altrnative outline on evoution

and some consequences concerning valuations

by

Gregor Kjellström

 

            References          

The fitness of the individual

Definition 6.1. s(x) is the probability that the individual having the parameter value x will be selected as a parent to  new individuals in the population.

In contrast to other earlier models of evolution (see Introduction), where the gene is supposed to be a unit of selection, this new model relies on the premise that selection primarily takes place on the individual level, and therefore a measure of the fitness of the individual is necessarily needed, because otherwise the selection of individuals will not be possible.

The advantage is that it will in principle take into account all interactions between genes and all contemporary environmental factors that may affect s(x); including the stroke of lightning. The phenotypes of the adult individual will be seen as a result of a DNA-message and some standard environment. Deviations from this standard will be regarded as a change of s(x). Thus, since we do not presume any particular structure or extension of s(x), the environmental factors have been ignored.

A disadvantage is that s(x) is a relative measure that can hardly be known for any individual, and that can only be estimated for an individual cloned in a very large number. Nevertheless, it can be used in mathematical models to examine certain properties of the evolutionary process. Even if s(x) of a particular individual is uncertain, the behaviour of mean fitness, determined over a large set of individuals, may as well be examined with fairly good reliability and even if this approach is of little practical use, it may have some philosophical implications. It also makes it possible to apply the theory of information, which is an abstract theory on probabilities only.

More generally:

Definition 6.3. The fitness of the individual has been defined by Hartl as the probability s(x) that the individual having the n characteristic parameters xT = (x1, x2, ..., xn) – where xT is the transpose of x - will survive, i. e. become selected as a parent of new individuals in the progeny.