Hi Bob,
On Sun, 26 Jan 2003 20:26:00 -0700, [EMAIL PROTECTED] wrote:
> I agree that some, if not all, of what Darwin observed was the results of
> natural selection. Since he observed the end results, I don't think it
> would be technically appropriate to call that *scientific fact* (since
> there was no reproducible series of controlled experiments). But, no
> doubt, he was correct that adaptation to environmental factors was at
> work in the environment. (I'm not disputing his observations, I'm just
> trying to use the correct words).
An observed fact is still a fact. Not to be confused with a
reproduceable experimental result.
<snipped>
> but a new DNA sequence
> cannot occur without a means to introduce the change.
Granted. :)
> Down's Syndrome is an example of a negative mutation (genetic change
> located at the Number 21 Chromosome).
This is a result of genetic damage. Sadly.
> Were it to have beneficial effects
> (to increase the competitive advantage of the individual) and to be
> reproducible through normal reproduction, then it would be a positive
> mutation.
Agreed.
> But, mathematically, neither can occur without somehow changing
> the DNA structure.
Mathematics is probably not involved. :)
> The evolutionary theories require both natural selection and genetic
> mutation. Creationists (of all varieties) and Evolutionists (of all
> varieties) would agree with the natural selection part (Mendelian
> Genetics). But, Creationists won't accept the (positive) mutation part
> and Evolutionists do. Therein lies the difference.
Genetic change is at the heart of evolutionary change, I agree.
And genetic change happens all the time. It can happen from being
hit by cosmic rays, by exposure to any number of chemical moities, by
the natural process of ageing, and so on. DNA is a most fragile thing.
But a genetic change does not get passed on, intact, to the next
generation if it is not present in the gametes, i.e. not heritable.
Example: Seeds of the privet, in seed trays by the thousands, look
for the occasional "sport" of a variegated seedling - genetic change of
single individual organism that makes the leaves bi-coloured. But seeds
of those "sports" breed back to the original plant stock,
i.e. non-variegated.
So that particular genetic damage/change is not heritable.
But sometimes the genetic change IS heritable, and future
generations of such organisms may carry the change. If it is a recessive
gene, it may not even be expressed. It may even disappear in the normal
shuffling of chromasomes during conception. But sometimes it holds the
change well.
If it is a tiny change, it may not make any difference and may well
disappear in the gene shuffle. A bad change will make it more likely
that such individuals will be at a disadvantage in the reproduction
game, and will not get to make many heirs and successors. A really bad
change may be lethal.
But some changes may just give the individuals a tiny advantage when
environmental changes occur - and the environment is ALWAYS changing -
so that small difference pays off, and is passed on. That is when
Darwin's "natural selection" sorts out the winners and losers, even when
the difference is minimal, and gives the winners just enough edge to
matter. They will then out-compete those individuals without that
genetic change, who may then go into decline.
If this happens enough times, and when the differences slowly
accumulate, the new individuals are eventually of a genetic profile that
they are no longer compatible enough with the original organism that
they cannot interbreed, then:
At that point, they are a new species BY DEFINITION.
This takes a long time, many many generations. But there has been a
long time since life appeared on earth, so that is not a problem unless
you believe in a "young earth".
Now, in such a drastic condensation of the subject, what have I missed ?
Or should I just say "RTFM" ?
Regards,
Ron
Ron Clarke
http://homepages.valylink.net.au/~ausreg/index.html
http://tadpole.aus.as
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