From: colby@bu-bio.bu.edu (Chris Colby)
Newsgroups: talk.origins
Subject: selection (response to Johnson)
Date: 24 Jan 93 01:20:00 GMT
Organization: animal -- coelomate -- deuterostome

In article <1jo29o$srt@agate.berkeley.edu> philjohn@garnet.berkeley.edu (Phillip Johnson) writes:
>I am not sure that it is possible to hold a discussion in this
>group, because the majority of participants seem to consider the
>neo-Darwinian theory to be so obviously true that doubt is not
>taken seriously.  On that basis, what is there to discuss?

If you, or your book, provided any reason to doubt neo-Darwinian theory,
we could discuss that. (BTW, "modern synthesis" is preferred to
"neo-Darwinism" these days -- no big deal, though.) Recent papers
by Cairns, Foster and Hall have caused me to reconsider (and reject)
one of the tenets of the modern synthesis. When I saw a good demonstration
that something was wrong with evolutionary theory, I changed my mind.
When I read _Darwin on Trial_, I just yawned.

[Mr. Johnson quotes from my FAQ]
>"The kind of evolution documented above [in the peppered moth
>example] is called "microevolution".  Larger changes (taking more
>time) are termed "macroevolution".  Some biologists feel the
>mechanisms of macroevolution are different from those of
>microevolutionary change. Others, including  myself, feel the
>distinction between the two is arbitrary.  Macroevolution is
>cumulative microevolution."

>This wording acknowledges that "some biologists" do not think
>that the peppered moth example illustrates a creative process
>that can produce new species, much less new complex organs. 

Not quite, I said "Some biologists feel the mechanisms of
macroevolution are different from those of microevolutionary
change." "The wording" doesn't _acknowledge_ (as if I'm trying to hide 
something -- the theme that biologists are hiding things from the public
runs through _Darwin on Trial_) anything; it says it flat out. Goldschmidt,
for example, thought mutations with large phenotypic effects were
a prime mechanism of macroevolutionary change. His evidence was
that the features exhibiting variation within the species he studied
were not the features that varied between species. More recently,
paleontologists such as Stanley, Gould, Eldredge and Vrba have
argued that "species selection" and/or "species sorting" may be
additional mechanisms of evolution that work at the macro level.
Their evidence is based on the geographic and stratigraphic distribution
of fossils. [My FAQ briefly explains punctuated equilibrium  
(known to many as "punk eek" and to some dissenters as
"evolution by jerks".) Species selection is the mechanism of
punk eek.]

The quote doesn't mention any biologist's opinion as to whether
natural selection is a creative process. Please explain why
natural selection would need to be a creative process in order to
be a major (or even the only) mechanism responsible for bringing about 
the pattern of biological diversity on earth. I don't think selection
is the least bit creative, but I believe it is the primary mechanism
responsible for bringing about, from a single common ancestor, all of
the species on earth and their phenotypic features.

>I would say that it is reasonable for a well-informed observer to
>conclude that macroevolution (i.e. the creative process that
>produced complex plants and animals in the first place) is not 
>"cumulative microevolution" (i.e. the peppered moth example writ
>large over geological time).

Some well-informed observers have concluded just that (Goldschmidt
and the others above, for example). Others haven't. As for myself,
I know of numerous cases where (micro)evolution has been brought
about by natural selection. These include changes in color (the
moth example), morphology (Darwin's finches, to name just one),
behavior (there's a paper in one the most recent issues of _Nature_
on natural selection altering the migratory behavior of a species
of bird) and biochemical traits (for example in the _Rhagoletis 
pomenella_ variants that are currently diverging from their
parent species.) Furthermore, I think macroevolutionary change
can be sufficiently explained by lots of different microevolutionary
changes. So, I see no need to postulate further mechanisms for
modification with descent; especially since selection has been
demonstrated to act in a wide variety of circumstances. Selection
has not been directly shown to bring about macroevolutionary change 
because of the time scale of human observation; but, I feel confident 
that any "macro" change could be split up into component "micro"
changes and that selection could be (or maybe even has been) shown to be
able to bring about that change in an analogous fashion.

>If so, it is also reasonable to
>conclude that the mechanism of macroevolution is an unsolved
>mystery.

Except that the biologists who claim microevolutionary mechanisms
are not sufficient to bring about macroevolutionary change have
posited new mechanisms. Their hypotheses make predictions that
can (and have) been tested. Goldschmidt's hypothesis is supported
only scantily by the data and the overwhelming amount of biologists
reject it. Gould and Eldredge's hypothesis has (IMHO) only equivocal
data and, as far as I gather, bean-bag geneticists think it sucks and
rock-hunters think it's the cat's meow.

>This does not necessarily imply supernatural creation,

Especially since there is no evidence for supernatural creation.

>because it is possible that science will discover a naturalistic
>mechanism at some time in the future. 

Could be.

>It is also not "anti-
>science."

Depends on what "It" is. If you mean asking if the mechanisms of
microevolution are sufficient to explain macroevolution, then
you are right. Finding out if other mechanisms are needed or
if they exist (and if they exist, how important they are in
comparison to microevolutionary mechanisms) is a very good,
unresolved scientific question.

>My impression is that many participants in this group think that
>the position stated in the preceding paragraph is unreasonable,
>and even in some sense reprehensible.  Is that correct?

No, just inane.

>If so, why?

Because it takes a lot of drive, talent and intelligence to come
up with scientific hypotheses(*); it takes about 4 brain cells to
say "every last detail isn't present, I don't believe any of it"
-- the impression I was left with upon reading _DoT_. The "I
don't believe any of it" stance seems all the more lame when it
is clear that the person doesn't understand what he is refusing to
believe in, or is asking for unattainable levels of proof as an
excuse to believe in whatever he wants. 

[(*) T.o-ers can say what they will about Velikovsky, at least the guy 
didn't just lamely refuse to believe modern science; he put forth his very
own hypothesis. Of course, it was ridiculous beyond description...]

One of the major themes of _DoT_ is that natural selection
could not possibly be responsible for bringing about new species
or complex subsystems of organisms. Would you like to expand on
that here (your post seems to be in that vein)? Or would you like 
to defend your position on common ancestry? I walked away from
_DoT_ with the idea that you doubted this. I think (as opposed to
your opinion as espoused in _DoT_) that evolutionary biology 
only gets better the more you know about it and I would welcome
the opportunity to discuss this with you.

BTW, in case you are wondering, I think common descent is a fact.
And (IMHO), the sufficiency of the natural selection theory can be argued for
by considering that fact, experimental demonstrations of selection
(including understanding what _exactly_ selection is and how it
works) and the lack of evidence for other mechanisms. 

>Phillip E. Johnson
>  School of Law, University of California, Berkeley CA 94720

Chris Colby 	---	 email: colby@bu-bio.bu.edu	---
"'My boy,' he said, 'you are descended from a long line of determined,
resourceful, microscopic tadpoles--champions every one.'"
 	--Kurt Vonnegut from "Galapagos"

Newsgroups: talk.origins