I.10.1 Natural selection and biological fitness are not tautologica

Natural selection andfitness are very closely related and are basically two sides of the same coin. Natural selection prefers individuals with greater fitness at the expense of those with lesser fitness. While this statement is true, it does not really provide us with any information if fitness is defined as the ability to survive in competition with other members of the population, i.e. as the ability to resist the action of natural selection. The opponents of Darwinism have frequently pointed out the fact that the definition of natural selection and the definition of fitness basically constitute a circular definition – a tautology. A favourite argument following from this is that Darwinism as a whole is a theory that cannot be proven false and thus is not scientific and is incorrect.

The relationship between falsifiability and scientific theory is somewhat more complex than the opponents of Darwinism usually realize (see XXVII.1.2 and XXVII.1.3). However, what is more important is the fact that these objections are based on a lack of understanding of the role of the term fitness in Darwin’s theory of evolution. As frequently happens with opponents, they attribute to the criticized theory something that it never stated. They argue that Darwin apparently stated that: “In biological evolution, the organisms with greater fitness survive; greater fitness is a property of those organisms that better withstand the action of natural selection.”

This is a fundamental distortion of the nature of Darwinism. In his theory, Darwin did not try to find a property that is increased during evolution and that would determine a tendency or direction of biological evolution. Such a property could theoretically be, e.g., mysterious fitness or a quite prosaic rate of reproduction, the overall mass of the members of individual species, the effectiveness of conversion of nutrients into biomass, i.e. the number of viable individuals per unit of consumed nutrients, etc. This undoubtedly very interesting aspect was not at the centre of Darwin’s interest and is quite outside the sphere of aspects that are the subject of Darwin’s theory of evolution. In contrast to, e.g., Larmarck, Darwin was not concerned with such a property and certainly not with its nature. He was only looking for a mechanism that could explain the development of organisms and also their gradual useful adaptation to the external environment. He used fitness only as a technical term, encompassing a range of quite specific and, under various circumstances, different properties affecting the chance of an organism to leave behind progeny and not as a special hypothetical property driving biological evolution like a motor.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.