natural selection, mutation, speciation (was peppered moth)

Ami Chopine (
Tue, 16 Mar 1999 11:02:19 -0800

David Tyler wrote:

The "Beak of the Finch" was in my thoughts as I wrote the above
comment. Here is yet another example of variation in nature, but
what do we really know about mechanisms? Is there any evidence that
genetic changes were occuring in these finches? We know that there
were environmental changes, but were the forces of natural
selection? I have only read of inferences.

I am asking:

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.

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?