Re: natural selection, mutation, speciation (was peppered moth)

David J. Tyler (
Wed, 17 Mar 1999 12:21:23 GMT

Ami Chopine wrote on Tue, 16 Mar 1999:

> By genetic changes, do you mean a shift in dominant attributes in the gene
> pool, or actual mutations? The difference is very meaningful.
> As we can see by the examples of the moths, the finches, dogs, roses, and
> other species which have been naturally, or intellegently selected, there is
> a very great range of attributes already present in a given species.

I was referring to mutations. Yes, great variations are possible
via natural or artificial selection which are not associated with
mutations and which therefore do not count as evidence for

> Natural selection is a very real force in determining which genetic traits
> become dominant. Natural selection is not in any way responsible for
> genetic mutations. It does, however, determine if those mutations are
> beneficial, neutral, or harmful.


> Another question is, and the finches contribute to this question much better
> than the moths: What does it take to become a new species?
> Mutations occur in every generation of any given species, and typically do
> not cause the offspring to become a different species. How much mutation
> and selection does it take to preclude a variety of finch from mating with
> another one?

Taxonomists name species - and there is not a consensus as to what
constitutes as species! Since we have plenty of examples of
intra-species and intra-genera hybridisation, the old definition of a
species being reproductively isolated is unworkable. Have we got too
hung up on "species"? To some of us, there are far more interesting
questions about taxonomic relationships to research!

Best wishes,
David J. Tyler.