III.4 Mutationism cannot explain the development of adaptive traits.

A certain modern variation of mutationism appeared at the beginning of the 1980’s in the work of G.A. Dover (Dover 1986)According to this author, organisms need not always be usefully adapted to their environment because natural selection would gradually select mutants that are increasing well adapted to this environment but also because the individual mutants actively look for an environment and a lifestyle for themselves in which their mutations are most useful in practice.At first glance, it might seem that this reversed evolutionary theory (adoption rather than adaptation) could actually work.However, appearances are deceptive.Active search for a suitable environment could explain divergence of the originally single species into many daughter species, differing in their body structure and environmental requirements, but could not explain the formation of adaptive structures.

            Any particular mutation (of evolutionary importance) must be either advantageous or disadvantageous for an individual in a given environment, or could be advantageous in one environment and disadvantageous in another environment.If a mutation were disadvantageous in all environments, then the mutant would die out.If it were disadvantageous in the original environment but would allow the individual to occupy a different environment, then a new species could be formed under favourable circumstances.However, there is no reason for expecting that its adaptive structure would be in any way better than that of the original species, it would simply be different – corresponding to the requirements of the new environment.The ability to explain the gradual systematic improvement of complicated adaptive structures is one of the greatest advantages of classical Darwinism.If the mutation were also advantageous for the individual in his original environment, a new species could again be formed that would, in some parameters be better than the original species (e.g. with better sight, faster legs).However, in this case, this would correspond to the development of a mutant and its descendants at the expense of the other individuals in the population, i.e. classical Darwinist evolution.

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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.