Re: morphological change

Brian D. Harper (bharper@postbox.acs.ohio-state.edu)
Fri, 9 Jun 1995 13:06:43 -0400

Jim Bell writes:

>Glenn writes:
>
><<Is there anything which would convince you that morphological transitions
>have occurred?>>
>
>A convincing critique of Wise and Johnson, which you have promised, would be a
>good start. A convincing argument from the evidence, which does not assume the
>answer would also be most helpful. You have assumed major transitions (for
>which we have few items of potential evidence) from minor change (abundant
>evidence). You have not yet explained why this leap is plausible for all of
>life when the list of problems is so vast.
>
>You have asserted "there are thousands of examples of gradual change in the
>fossil record." You then leap to the conclusion of large scale change (major
>transitions).
>
>But Wise looks at the claimed evidence and asserts, "the total list of claimed
>transitional forms is very small..." (TCH pg. 227). He explains why. Then:
>"Transitions from one major group of organisms to another are challenges to
>the ingenuity of even the most capable macroevolutionists."
>
>Feeling ingenious? I'd like you to explain to Kurt and me why he is wrong.
>

Sorry to butt in, but it seems to me that many of the complexity
folks would be more likey to agree with Kurt and Jim than with
Glenn. Consider the following excerpt from the preface of Goodwin's
book:

Here we face another curious consequence of Darwin's way of
looking at life: despite the power of molecular genetics to
reveal the hereditary essences of organisms, the large-scale
aspects of evolution remain unexplained, including the origin
of species. There is "no clear evidence ... for the gradual
emergence of any evolutionary novelty," says Ernst Mayer,
one of the most eminent of contemporary evolutionary biologists.
New types of organisms simply appear upon the evolutionary
scene, persist for various periods of time, and then become
extinct. So Darwin's assumption that the tree of life is a
consequence of the gradual accumulation of small hereditary
differences appears to be without significant support.
Some other process is responsible for the emergent properties
of life, those distinctive features that separate one group
of organisms from another--fishes and amphibians, worms and
insects, horsetails and grasses. Clearly something is missing
from biology. It appears that Darwin's theory works for the
small-scale aspects of evolution: it can explain the variations
and the adaptations within species that produce fine-tuning of
varieties to different habitats. The large-scale differences
of form between types of organism that are the foundation of
biological classification systems seem to require another
principle than natural selection operating on small variations,
some process that gives rise to distinctly different forms of
organism. This is the problem of emergent order in evolution,
the origins of novel structures in organisms, which has always
been one of the primary foci of attention in biology.

It is here that new theories, themselves recently emerged within
mathematics and physics, offer significant insights into the
origins of biological order and form.
...
[goes on to discuss the emerging science of complexity--BH]

-- Brian Goodwin, _How the Leopard Changed Its Spots_,
Charles Scribner's Sons, 1994, p. viii - ix (preface).

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Brian Harper | "Do not conclude from your apprenticeship |
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