Re: Are there any other mechanisms for Evolution

On 7 Apr 2006 17:15:25 -0700, "Freshwater Spaceman"
<Interplanetary.Pirate@xxxxxxxxx> wrote:

Hi,

I'm just wondering if there are any other mechanisms (without divine
intervention) for evolution, other than natural selection? I can't seem
to find anything on the web.


Traditionally, the way it is taught in many evolution books follows
from the definition: evolution is a change in the genetic composition
(allele frequencies) in a population over generations. The next step
is to review the notion of a Hardy-Weinberg equilibrium that states
that with a large population, random mating, no migration, no
mutation, and no selection, then the expected value of the gene
frequency does not change over generations. That is, there is no
evolution. From that it follows that any violation of the assumptions
on the Hardy-Weinberg equilibrium are potential mechanisms of changing
gene frequencies, hence of evolution. They are:
1) Small population, otherwise called drift, with special cases
being bottleneck effects and founder effects
2) Non-random mating, sometimes confounded with sexual selection
3) Migration, also called gene flow
4) Mutation. This is generally considered so infrequent that it
causes only tiny changes in gene frequency and hence it is not an
important effect. On the other hand, it is the source of all new
alleles and variation and hence it is the ultimate cause of all
evolution. So it is simultaneously the most important and the least
important!
5) Natural selection: the ability of different genotypes to make
different contributions to the gene pool of the next generation.

Of these, generally drift and selection (of all varieties: sexual,
natural, and artificial) are the ones really considered. Mutation is
a side issue to be discussed separately and migration usually
stabilizes populations, making otherwise separated small populations
appear more like a single large population.


.

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