From: swf@teradata.com (Stanley Friesen)
Newsgroups: talk.origins
Subject: Re: some more stuff about fruit flies
Date: 13 Oct 92 02:00:47 GMT
Reply-To: swf@tdat.teradata.com (Stanley Friesen)
Organization: NCR Teradata Database Business Unit

In article <98267@bu.edu> colby@bu-bio.bu.edu (Chris Colby) writes:
|In article <7228@tekig7.PEN.TEK.COM> alanf@tekig6.PEN.TEK.COM (Alan M Feuerbacher) writes:
|>Then Fix talks about Richard B. Goldschmidt's observation [possibly in
|>_The Material Basis of Evolution_, 1940] that mutations in fruit flies
|>    were all so incredibly micro that even if a thousand were combined
|>    in one specimen, it would still not amount to a new species.
|
|Goldschmidt was a proponent of saltationary evolution -- evolution
|via the hopeful monster. The primary data for his theory was that
|characters that varied within species of [whatever clade of organisms
|he studied, moths I think, but don't quote me] were different from
|the characters that varied among species. Fix is ignoring the fact
|that evolution works by cummulative selection, not mass mutation.
|He therefore has latched onto a legitimate scientist's argument and
|distorted it to serve his own purpose. What he neglects to mention
|is that Goldschmidt's theory is not well accepted, and that his
|statement regarding fruit flies is simply ignoring how scientists
|propose evolution works.

Goldschmidt was pretty well blown away by the work of such men as Ernst
Mayr, Stebbins, Huxley (the younger one), and others.  He was pretty
well finished, scientifically speaking, by 1950.  Nowadays he is usually
presented as a well-intentioned boob (undeservedly - the evidence prior to
the 40's and 50's was ambiguous - but nobody pays much attention to him
today *except* Creationists).

|>    If we are drawing conclusions about man's evolution using DNA
|>    comparisons, we then have to do a lot of explaining about those
|>    variations found in nearly identical frogs.
|
|Here Fix is just plain confused, DNA sequences are used to construct
|phylogenies. They are not used to in "drawing conclusions about
|man's evolution", at least not conclusions other than his relations
|to other primates. Variation within and among species does not need
|to be mirrored exactly in morphology. There is plenty of "junk" DNA
|in the genome that is free to vary without inducing phenotypic
|changes in the organism. Likewise, small changes in regulatory genes
|can cause large changes in phenotype. ...

In fact the latter is considered to be of major importance by most modern
researchers.  I would suggest that Alan read a little Ernst Mayr, he
*frequently* points out this little 'discrepency' between amount of DNA
change and amount of morphological change.  [And don't make a mistake here,
Ernst Mayr was one of the architects of the 'New Synthesis' - the modern
form of the theory of evolution - so he is hardly claiming this is a
problem, in fact it is one of the facts he incorporated into the modern
theory of evolution].

|>    The author of virtually every
|>    contemporary book supporting evolution trots out the human-chimp
|>    DNA comparison, but very few mention the frogs or another
|>    discovery of microbiology that has been known for some time.
|
|I've heard the frog story numerous times, what about it does Fix
|think contradicts evolution? The frogs simply have accumulated a lot of
|neutral variation while staying morphologically similar -- humans and
|chimps, on the other hand, have diverged phenotypically but have done
|so without accrueing much variation.

Indeed, this may be evidence that frogs have been around longer than
mammals.  (Hmm, interesting, I believe that is pretty much what the
fossil record indicates too ...)

|>	[Speaking about homology]. Now if these various
|>	structures were transmitted by the same gene-complex, varied
|>	from time to time by mutations and acted upon by environmental
|>	selection, the theory would make good sense.  Unfortunately
|>	this is not the case.  Homologous organs are now known to be
|>	produced by totally different gene complexes in the different
|>	species. 
|
|Bullshit, where's Fix's evidence for this? If this were true, it
|would indeed be a big problem for evolution. 
|
|[his reference for this claim]
|>	[Randall, John L., _Parapsychology and the Nature of Life_,
|>	New York: Harper & Row, 1975]
|
|A parapsychology text? Gee, I don't know if that constitutes
|evidence. I'll wait and see what my psychic astrologer says first.
|Has the National Enquirer come out with an opinion on this?

Eeep!  Yeah, well no wonder I never heard of this 'fact' either. :-)
Only parapsychologists know it.

Now, there are many situations where identical 'structures' exist that
are not homologous, but always where the structure involved is simple,
or constrained by other factors.  The most common examples I know of
are plant secondary products (steroids, tannins, and so on).  Amoung
these chemical are many that are indeed made by different pathways in
different groups of plants.  But this is *invariably* taken as evidence
of independent evolution of the same chemical, and thus *not* homology.
[And since these chemicals are constrained by the laws of chemistry, and
are exceeding simple compared to most biological molecules, such convergence
is not really that surprising].

|>    If the results of these experiments is true, it seems to me to
|>    imply that at least some of the DNA has some sort of
|>    error-correction function, true or false?
|
|How about going to the library, picking up a genetics(*) text and
|finding out for yourself? There are certainly mechanisms that
|correct base pair changes during replication and in response to
|mutagens, but that doesn't seem to be the question you are asking.
|
|(*)Try Watson, et.al., 1987, Molecular Biology of the Gene, Benjamin/
|Cummings, Manlo Park, California. See especially chapter 12 "The
|mutability and repair of DNA" and chapter 22 "The molecular
|biology of development" (homeotic genes are discussed here).

Ah yes, the latest edition of that grand old classic.
[I first cut my scientific teeth on an older edition of this book, it
was *excellent*, if this edition is as good, I heartily recommend it].
[Oh, from what I have seen, it is *massively* updated - nearly 50% larger,
and covering subject that were not in the older edition].


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  or
Stanley.Friesen@ElSegundoCA.ncr.com