[net.religion] Evolution and the Fossil Record

janc@uofm-cv.UUCP (10/28/83)

Quoting Ray Davis:

> I always wondered where the fossils of the transitional creatures
> went.  You can find lots of prehistoric monkeys, lots of cavemen,
> and lots of modern men, but where are the fossils of the creatures
> that slowly evolved from one step to another.

I think I can clarify this a bit, but first I should point out, that the
details on how specization happens are currently hotly debated among
evolutionary biologists.  It is generally accepted, however, that the
new species only develop only under very special conditions.  You don't
have to be an expert in evolutionary science to be able to see that a new
species can only develop when:

   (1) A population is isolated which is neither too small to have the
       necessary amount of natural variation, nor too large for changes
       to spread through the population.

   (2) There must be conditions which place the population under enough
       stress so that modified individuals have a significant advantage,
       but not under so much stress that the population is wiped out.

Naturally, such a situation rarely arises, but when it does, change
proceeds (in an evolutionary sense) fairly quickly.  The result is that
evolution does not happen slowly and continuously.  Instead, species
stay unchanged for long periods of time, then, when the right conditions
prevail, they change comparatively rapidly.

Now consider the fossil record.  From the period when men were evolving
from ape-like forms, we have fossils from maybe a dozen sites, randomly
scattered over a period of millions of years.  The odds are very small
that we would see a transitional form, since they aren't around long, and
are confined to limited geographic regions in small populations.

Imagine an analogy:  I mount a camera over your terminal, and take a
ten pictures at random intervals over a year.  I get pictures of you,
and I get pictures of your empty chair.  I'm not likely to see you
getting in or out of your chair.  I can conclude that you don't 
customarily spend two or three hours inching into your seat.  But can
I conclude that you appear there every morning in a *PUFF* of smoke?
Though I can't disprove that theory, I'd need much more finely spaced
it.

Both a theory of continuous creation (God make a new species every now
and then) and evolution are in agreement with the human fossil record.
However, I believe there are examples of the kind of evolutionary change
I have mentioned in the case of bivalves (clams), from regions where
there is a more complete fossil record.

					Jan Wolter
					University of Michigan
					Ann Arbor Michigan