[asa] chromasome fusion #2

Apparently chimpanzees, and other primates, have 48 chromosomes
while humans only have 46.

From an evolutionary standpoint this is suppose to be a problem.
Why is that?

It is presumed that chimps and humans have a common ancestor.
So I suppose the reasoning is that if one ancestor of the
common ancestor has 48 chromosomes and another has 46 there
is a problem in believing they had the same ancestor.

The reasoning might be that since chromosome number is
directly related to inherited traits that it might be
difficult to see how an ancestor with 48 chromosomes could
produce (in no matter the number of steps) an offspring
with only 46.

Now I, being naive, don't see why this is suppose to be so
great, or insurmountable a problem.
After all, if evoultion is correct, something like this must
be commonplace. Presumably the earliest of creatures had fewer
chromosomes than later species. So somehow chromosomes must be
added and I'm not certain why it should any more mysterious how
chromosomes can be added than that they can be taken away.

In any case, Ken Miller asserts that this is so great a problem that
unless it were resolved evolution must be wrong.
I am astonished by this statement and can hardly believe that he really
means it. In fact, it seems far more obvious that the reason he
says this is because he believed at the time of the statement that a
resolution was already at hand.

In any case, the resolution supposedly is that the second chromosome fused
with another chromosome, and since chromosomes come half from each parent,
this would result in 46 chromosomes instead of 48.

All I want to say about the supposed evidence that a chromosome had fused
is that it does not entail that evolution occurred, rather it is merely
consistent with an evolutionary development.

The story, I suppose, would be something like that the ancestor of both
man and chimp has 48 chromosomes, but somehow one chromosome in man
became fused to another, while that of the chimp and other primates did
not.

The notion of fused chromosomes is not necessarily associated with an
evolutionary process, unless one means by evolution that something
that existed previously was used in the creation of something new.
Such a view of evolution could as well be the work of an intelligent
designer, which is why I am confused by Ken Miller's apparent
confidence that evolution is clearly a superior explanation.

The very notion of fusion appears to entail a process whereby something
changed from not being fused to being fused. The notion appears to
entail that there was a time when they were not fused and somehow became
fused. It is true that if we presume that such processes must take place,
then fusion would be consistent with that presumption. But does the
evidence for fusion really entail that a fusion has taken place?
In order for fusion to have taken place we must have a time when
they were not fused. But the mere fact that they appear to be fused
does not entail that they were ever not fused.

It seems then that here, as in all of science, we proceed abductively,
from theory to evidence and then back again to theory.
But in all cases the science finds a theory that is consistent with the
evidence. There is no way to argue from the evidence to a unique
theory. The supposed discovery of the fusion of chromosome #2 is
consistent with an evolutionary story, but it could just as well be
consistent with other theories and explanations. This is, of course,
true of all our knowledge of the physical world.

What is surprising to me is that some think that this discovery is
of great importance. Yet it seems to me that the result is more
or less assured by the supposed discovery that chimp DNA and
human DNA are so very similar.

I do not understand, I confess, why chromosomes are so important.
It seems to me that they are mostly an artifact from an earlier
state of biological science. Hence, I don't understand why fusion would
seem so important. But, then again, I probably don't understand why
the bunching of DNA that can be observed under a microscope should be so
important.

bill

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Received on Sun, 12 Jul 2009 19:55:41 -0600