Re: Mutationism Redux
- From: Bill Morse <wdNOSPAmorse@xxxxxxxxxxxxxxxx>
- Date: Sat, 19 Jan 2008 17:51:35 -0500 (EST)
Arlin wrote:
Read the last paragraph of my follow first. After you have responded to
that, we can continue to fight over the rest of it :-)
On Jan 17, 1:34 pm, Bill Morse <wdNOSPAmo...@xxxxxxxxxxxxxxxx> wrote:
Discontinuity: As has been oft noted, the extent of discontinuity depends
heavily on scale. At the lowest scales, change is clearly discontinuous,
simply because of the way genetics works. I think it also true that much
of observed variation is incremental, and remember that both Darwin and
Mayr had encyclopedic knowledge of biology. So if they both espoused
theories that were based on incremental change, I will be slow to accept
a theory that argues otherwise.
Bill, I scarcely know how to respond to such an authoritarian
argument, other than to repeat that my characterization of the status
of infinitesimalism is based on a contemporary scientific analysis
that I cited. The infinitesimalist argument (specifically the
empirical side of the argument) has two parts: 1) show that
differences between closely related species are composed entirely of
infinitesimal changes and 2) extrapolate from this to all evolved
differences. The problem is that *the facts never allowed the first
step*. Orr and Coyne, 1992, systematically review the results of
quantitative analyses on this very question, and they write "We
conclude-- unexpectedly-- that there is little evidence for the neo-
Darwinian view: its theoretical foundations and the experimental
evidence supporting it are weak, and there is no doubt that mutations
of large effect are sometimes important in evolution." Furthermore,
they conclude that the MS architects *given the evidence available to
them at the time* were not justified in their conclusions either.
Without reading Orr and Coyne, I will note that at the time of both Darwin's
writing and of Mayr's contribution to the MS (and to a great extent today)
for most evolutionary change there is simply not enough of a fossil record
to tell whether differences between closely related species are composed of
incremental changes. And Orr and Coyne in the quote you cite only say
that "mutations of large effect are _sometimes_ important in evolution."
One can look at the work of Axel Meyer on the cichlid fishes of the rift
valley lakes of Africa and see the power of selection using only
incremental change. I also note that you did not address the question of
the gene pool, and I don't know if Orr and Coyne discuss this. But given a
significant population size, the shared gene pool will in fact serve to
enforce incremental change. There are cases where this influence will not
be important, and Mayr acknowledged them using the explanation of founder
effect. So I think you may be exaggerating the emphasis on incrementalism
by the MS, even if you are correct on their rejection of mutationism as a
cause of large changes.
Now as to the conclusion of Orr and Coyne that the MS architects were
unjustified even given the available evidence, does this relate to my
argument (you snipped it from your follow) that the large changes between
clades should have given pause to the MS architects? This I think is the
telling evidence for the MAAD argument, but you do not even discuss it.
A scientist simply does *not* have the choice to ignore this kind of
hard quantitative empirical evidence in favor of generalizations from
dead authorities. Darwin's knowledge may have been "encyclopedic"
150 years ago, but it was neither quantitative nor even systematic by
modern standards. As Lord Kelvin said in a statement often quoted by
scientists (at least by the ones who value rigor) "When you can
measure what you are speaking about, you know something about it; when
you cannot measure it ... your knowledge is of a meager and
unsatisfactory kind".
I was not citing the dead authorities because of their generalizations, but
because of their extensive familiarity with the "hard quantitative
empirical evidence". I have already admitted that I am at a disadvantage in
this argument, because I haven't read Orr and Coyne. I have read both Mayr
and Darwin, and they both clearly know what they are talking about. I have
read your article, and you clearly know what you are talking about. If you
read my comments carefully, you will find that for the most part I agree
with you. I do think in the article you have portrayed the MAAD argument as
being in opposition to the Darwinian and MS position rather than explaining
how the MAAD argument clarifies their positions.
Creativity: I really don't want to touch this one. Sorry, Arlin, but the
language is too easily confused with creationism. And I don't think
mutation etc. is creative in any useful meaning of the word. The whole
point of evolution by natural causes is that no creativity is required.
First, I did not invent this issue of creativity-- its been part of
evolutionary discourse for 150 years.
Agreed - but you just said above you didn't like arguments from
authority ;-)
The notion that "natural
selection" is "creative" is a well established doctrine that is
referred to *explicitly* again and again in writings of the MS, as
documented by Gould in Ch. 4 of "Ever Since Darwin" (1977) and in his
giant 2002 book. Here is what Gould says (p. 44 of Ever Since Darwin,
1977)
"But why was natural selection compared to a composer by Dobzhansky;
to a poet by Simpson; to a sculptor by Mayr; and to, of all people,
Mr. Shakespeare by Julian Huxley? I won't defend the choice of
metaphors, but I will uphold the intent, namely, to illustrate the
essence of Darwinism-- the creativity of natural selection. Natural
selection has a place in all anti-Darwinian theories that I know. It
is cast in a negative role as an executioner, a headsman for the unfit
(while the fit arise by such non-Darwinian mechanisms as the
inheritance of acquired characters or direct induction of favorable
variation by the environment). The essence of Darwinism lies in its
claim that natural selection creates the fit. Variation is ubiquitous
and random in direction. It supplies the raw material only. Natural
selection directs the course of evolutionary change. It preserves
favorable variants and builds fitness gradually. In fact, since
artists fashion their creations from the raw material of notes, words,
and stone, the metaphors do not strike me as inappropriate."
That dog won't hunt. The above quote makes it very clear that the argument
for the "creativity" of natural selection is simply a reaction to
creationism. In another two hundred years the argument will have
disappeared, and the sooner we hasten its demise the better. Stop using the
term. We in fact are only currently using it for "superficial" reasons.
Second, we could all agree to stop using the word "creativity" for
superficial reasons, but we cannot choose to ignore the issue of how
to account for the origin of novelty, which remains an issue of great
interest to evolutionary biologists (e.g, type "origin of novelty"
into PubMed). So, saying that "no creativity is required" is a
rhetorical gesture that solves nothing.
Well again you snipped my actual argument, which is that the origin of
novelty is adequately described by "initiative" and "directionality", with
no need for use of the term "creativity". If you want to respond to my
_actual_ argument as to why "creativity" has some special merit despite its
linguistic baggage, I will be happy to respond.
Directionality: I should discuss this using the math, but even though it
was kept at a simple level I don't do it enough to completely understand
it.
The maths are there for the sake of rigor (to prove to skeptics that
there is a population-genetic basis for the effect), but they are not
needed to understand the intuitive concept of "first come, first
served".
I followed this with what I thought were the items most useful for further
discussion, namely how the MAAD applies to some questions that the MS
doesn't address. No comments on these? I would rather see replies to these
than to further quibble on your basic thesis, which I actually agree with.
--
Yours, Bill Morse
.
- References:
- Mutationism Redux
- From: Bill Morse
- Re: Mutationism Redux
- From: Arlin
- Mutationism Redux
- Prev by Date: Re: Symmetry of DNA replication
- Next by Date: Natural selection vs mutation - in the news
- Previous by thread: Re: Mutationism Redux
- Next by thread: Re: Mutationism Redux
- Index(es):
Relevant Pages
|
