Posted: May 22, 2010 10:56 pm
by Leonidas
Frozen plasticity theory
This theory suggests a mechanism of the origin of adaptive traits in sexual organisms. The classical Darwinian mechanism of the origin of adaptive traits by natural selection can explain the evolution of such traits only under a very special situation, e.g., in a genetically homogeneous population of asexual organisms.

A misunderstanding here and a big one. Darwinian evolution does NOT say that adaptive traits originate by natural selection. Natural Selection acts on naturally occurring variation. Darwin did not know the cause of that variation. We now know about mutations and DNA. Mutant genes arise due to faulty replication of existing genes. This usually produces a faulty gene which either kills or handicaps an organism. But sometimes a mutation is advantageous. Natural selection determines whether a mutant gene dies out or is propagated.

The frozen plasticity theory suggests that sexual species can evolve new adaptations by accumulation of random mutations only when their members are genetically uniform, i.e., only after a portion of the population of the original species has split off, balanced on the edge of extinction for several generations, and then undergone rapid expansion.

This confuses mutation with speciation. Mutations occur and spread through a population all the time. Even disadvantageous mutations can survive for a time, especially if there is a non-handicapped heterozygote. A famous example is the haemophylia gene that came from Queen Victoria and was passed onto many of her descendants in the royal families of Europe, including the son of the last Tsar of Russia.

For speciation to occur there does have to be reproductive isolation of two populations. This means that neither population can pass on mutant genes to the other. Eventually the two populations will be very different. Near extinction is not necessary, just sustained isolation.

After a short period of time, corresponding to 1-2% of the duration of the species (estimated on the basis of paleontological data), polymorphism accumulates in the gene pool due to frequency-dependent selection; and thus, in each generation, new mutations occur in the presence of different alleles and therefore change their selection coefficients from generation to generation.

I don't know about the numbers but basically isolated populations drift apart. That is standard evolutionary theory.

The species ceases to behave in an evolutionarily plastic manner and becomes evolutionarily elastic on a microevolutionary time-scale and evolutionarily frozen on a macroevolutionary time-scale. It then exists in this state until such changes accumulate in the environment that the species becomes extinct.

Sounds like gibberish to me, but then I have not read the full explanation. WHY is a question that immediately occurs. What is the mechanism for this declaration or is it no more than a declaration? The next point is that if a species becomes extinct due to being unable to cope with a changed environment then that also is standard evolutionary theory, natural selection and all. Most species become extinct without leaving descendants.