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Of course, this is not the definition of natural selection, and it is not the definition of fitness.

Natural selection is the survival of those that survive. If natural selection means "survival of the fittest," and the fittest are those that survive, then (they insist) the definitions are circular. The central theme of this chapter is a common creationist assertion that natural selection is invalid because it is circularly defined. By shifting from a focus on heritable traits to individuals, EE obscures the way in which biologists employ the concept of fitness, and mislead students. Įxplore Evolution misdefines this key biological concept, stating that fitness is a property of an individual, and is measured by that individual's contribution to future generations. Fitness then is the contribution of the average individual with that trait to the next generation. Thus, it is a property not of a single individual, but of a collection of individuals who share certain heritable traits.

While philosophers continue to argue about the best way to define "fitness," there are some generally accepted aspects of biological definitions of fitness.įirst, it is a term applied to an allele or genotype, a particular form of the genome. The biological concept of "fitness" is critical to an understanding of natural selection and of evolution in general.