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[Phys-L] Re: Another attack on Evolution



"So it is clear that even though there are only changes within a
species, this can lead to new species IF WE WAIT LONG ENOUGH *."

This [long enuf] is an analytic statement, therefore, that argument is invalid.

I was told different species can't produce fertile offspring. I suspect in the course of change a time comes when there are two lineages that, tho mating would be successful, don't mate because they "look ugly" to each other (metaphor). At this point change will accelerate to the point they are "really" different species.


* The time, I would think, varies considerably with species. Recently,
an approximate time for human evolution has been found, because
mitochondrial mutations occur at a constant rate. The article below is
instructive:


http://www.actionbioscience.org/evolution/ingman.html

bc

p.s. "From this study, a date of 171,500 years ago was obtained which
fits remarkably well with that proposed in the recent African origin
hypothesis." My, my such precision. I question it.

Hugh Haskell wrote:

At 16:38 -0500 1/21/06, Justin Parke wrote:


The problem as I see it is that while honest people do not dispute
that evolution (i.e. changes within a species) occurs it has not yet
been established to anywhere near the same level of indisputability
that all species evolved from a single or a few common ancestors. I
think your logical progression is misleading in that it assumes that
since change within a species has been observed that all other
postulates of evolutionary theory are therefore true.



In the first place, if "all other postulates of evolutionary theory"
follow from the observation of change with time within a species,
then they are not postulates, but conclusions.

But that issue aside, let's look at how evolution proceeds. There are
*only* changes within a species, since no parent ever gives birth to
something which is a new species. *Every* offspring looks largely
like its parents, even like its grandparents.

But go back 1000 generations, say, or 10,000, and you will see that
the newborn offspring may not resemble its ancestor of 1000 or 10,000
generations by nearly as much as it resembles its parents, and if you
look at two separate lineages of this ancestor after 1000 or 10,000
generations, those of one lineage may not even look much like
offspring in the other lineage, even though they share a common
ancestor. In other words, at some indistinct point in that chain of
1000 or 10,000 generations (maybe a lot more or somewhat less,
depending on the species and the circumstances) the two lineages
developed differences significant enough that they could be
designated as different species. This is how one can conclude (not
hypothesize) that new species emerge, based on the observed changes
over a large number of generations. This conclusion is in accordance
with the observed fossil record. And the process is easily extended
to any level of taxonomy. The general rule is that the farther an
offspring deviates from an ancestor, the longer the chain of
generations between ancestor and offspring.

So it is clear that even though there are only changes within a
species, this can lead to new species if we wait long enough.

I think this is the sort of fact that John D had in mind when he made
his comment (but only he can confirm my conjecture).

This brings up the point that biological taxonomy is a structure
imposed upon the observational data by human scientists, not
something that exists in nature apart from human observation. The
boundaries between taxa are fuzzy and indistinct and often subject to
vigorous debate among biologists and taxonomists. However, we can be
sure that we will never see an offspring of a different species than
its parents. The process of an emerging new species is slow and
gradual, and although we may be able to assert that the offspring in
the 1000th or 10,000th generation constitute a new species, we can
never pin down the exact location of that boundary, and in fact there
is *no* location for that boundary, since no parent ever gives birth
to a new taxon at any taxonomic level.

It is exactly the same as when you look at a color wheel. It is
clear, for example, that one part of a color wheel is green. Everyone
can agree with that (unless they are color-blind). And about a third
of the way around the wheel, the color is blue. Everyone will agree
with that (even most color-blind people will be able to agree that
the blue part of the wheel is different from the green part). But is
is impossible to pin down the exact point where the green becomes
blue. The change from point to adjacent point is so nearly continuous
that it is impossible for us to distinguish between them. Yet nobody
disagrees that green can morph into blue if you make the appropriate
changes to the color balance, even though nobody will agree on just
where the boundary is between the two.

Please note, that I am not claiming that taxonomy is isomorphic with
a color wheel. I'm only making an analogy about boundaries.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

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