Re: Is evolution really the central theory for all of biology?

From: David C Campbell <amblema@bama.ua.edu>
Date: Wed Sep 14 2005 - 12:29:56 EDT

>>For instance, Darwin hoped we would discover transitional
>>precursors to the animal forms that appear abruptly in the
>>Cambrian strata. Since then we have found many ancient
>> fossils - even exquisitely preserved soft-bodied creatures - but
>>none are credible ancestors to the Cambrian animals.

>While others can speak the topic more expertly than myself, I think
>Dr. Skell is wrong where he says no credible ancestor exist for
>Cambrian organisms.

Yes; the misrepresentation of the Cambrian radiation as a problem for
evolution is paleontologically inexcusable, apart from the caveat that
Gould's claims of extreme randomness (which overestimated the diversity
and disparity) are partly responsible. Many of the exquisitely
preserved soft-bodied forms are not credible ancestors to the Cambrian
forms, because they are well after the Cambrian and much more advanced.
 However, there are Precambrian fossils that are plausible ancestral
forms, and many of the Cambrian fossils themselves show transitions and
are good ancestors for major groups.

There is a big increase in the number and kinds of things with durable
skeletons at the beginning of the Cambrian, and widespread
environmental changes seem to have provided a unique opportunity for
soft part preservation, so the Cambrian record is much better than the
Precambrian record.

Certainly there are aspects of the Cambrian radiation that are still
being investigated, and the Precambrian fossil record is a very active
area of research as well.

Simon Conway Morris has detailed discussions of the topic, being an
expert in the Cambrian as well as a Christian; a much shorter
discussion is in Miller's Perspectives on an Evolving Creation.

>> most can conduct their work quite happily without particular
>> reference to evolutionary ideas

My own field is paleontolgoy and evolutionary biology, so evolution
pervades my everyday research, as well as that of my immediate
colleagues.

Everything in biology only makes sense in the light of evolution is
true only in the sense of "everything at once". You can turn on a
light switch without having a clue about electricity, but if you want a
full understanding of what's happening, you need knowledge of basic
physics. Likewise, I can count animals without worrying how they got
that way, but if I want to make sense of the numbers, I must have some
idea about the factors that influence animal populations, and these tie
directly into evolution. Again, medical testing can be done on an ad
hoc basis of "this works OK", but evolution provides a number of basic
explanations, such as (a) due to their common ancestry, organisms have
basic biochemical and physiological similarities, with greater
similarity closely reflecting the degree of relatedness. Thus, testing
medical procedures on animals, especially primates, is expected to be a
good proxy for humans. (b) features of humans reflect their
evolutionary heritage as well as their current environment, so some
adaptations for past conditions may be problematic now (e.g., ability
to consume a lot of food in case of irregular availability becomes a
problem in times of ready availability; sturdy teeth for raw food gives
orthodontists opportunities now that our skeletons as a whole are
becoming less massive, including the jaws; our backs have only a few
million years of mainly upright use and are not as strong as we think
when trying to lift heavy stuff) (c) disease organisms are in a tight
competition to defeat the body's defenses enough to survive and
reproduce without doing so much harm as to kill the host before the
disease can be transmitted. Thus, pathogens are likely to respond
rapidly to challenges (new antibiotics, etc.), and the really deadly
stuff will be things that normally infest other organisms and
accidentally get into us (bird flu, ebola, larval tapeworms, etc.) (d)
Cancer, to survive, must constantly evolve ways to evade the body's
controls and defenses. (e) People are strongly inclined to act in
their own selfish interests and have a drive to reproduce.
Expectations of human behavior and likely means of disease transmission
that do not take these into account will probably be wrong. (f) other
things I haven't thought of off the top of my head.

Evolution is a uniting theory for all of biology, allowing us to
connect every aspect of it into a coherent framework. While working on
the details, it's not always necessary and may even be distracting to
focus on it, just as in the example of using Newtonian physics rather
than a more accurate and fundamental but more complicated relativistic
calculation in dealing with spacecraft launches.

----------------------------------------
Dr. David Campbell
425 Scientific Collections
University of Alabama, Box 870345
Tuscaloosa AL 35487
"James gave the huffle of a snail in
danger But no one heard him at all" A.
A. Milne
Received on Wed Sep 14 12:31:52 2005

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