From: Josh Bembenek (jbembe@hotmail.com)
Date: Sat Oct 25 2003 - 12:20:15 EDT
Denyse-
Let me start by saying that Wells criticism was right in that there are
incongruencies. But let's not overlook some very interesting science. The
impression that Wells gives to some extent is that due to incongruencies,
the whole tree of life idea is quite tenative. But this is not the case,
just as we see that many species of fish have fins on their back, we should
expect that there is a consistent and common genetic basis for this
phenomena. Homologous things, whether designed or evolved, are expected to
resemble one another not only in phenotype, but also in genotype. I think
the whole criticism is off track for this reason, we should not expect
things that operate in very similar ways to be reinvented in each and every
organism. How you interpret this conservation, either a common blueprint
derived in the mind of an IDer or a conserved set of functionality passed on
through common descent is another issue- but there should and will be more
and more conservation observed. The tree of life is not some willy-nilly
disorganized idea that isn't really supported very well.
Let's consider the 2001 Nobel prize awarded in the cell cycle field. Paul
Nurse was one of the winners, and his discoveries were very important for
science in general, and the cell cycle in particular. Check out this fairly
easy pdf (I just serched google for Cdc2, Paul Nurse, and conservation):
www.ias.ac.in/resonance/Feb2002/pdf/Feb2002p46-54.pdf
Here's the relevant quote:
Paul Nurse works at the Imperial Cancer Research Fund, London, UK and
is the Head of ICRF. Using the fission yeast as a model, he identified and
characterized the mode of function of the CDC2 gene. He showed the
strong conservation of this gene from humans to yeast, thus demonstrating
the remarkable conservation of this mechanism. He then elucidated
the regulation of the activity of this protein and its role in cell cycle
phase
transitions. He has received the Gairdner Foundation International Award,
The Albert Lasker Basic Medical Research award, which he shared with
Hartwell and Masui.
Basically, these pioneers discovered a whole collection of genes in yeast
that were essential for the organism to successfully complete cell division.
They discovered that one of the most important genes required for cell
division was conserved. That means that you can take a yeast cell, and
remove the gene. The removal of this gene causes yeast to die. You can
then take the human gene and replace the lost yeast gene IN YEAST, and the
yeast cells grow normally. This was a landmark discovery: the same subset
of genes that govern cell division in fungal cells operate in human cells
and they can be interchanged! This means that every time God made an
organism, he didn't reinvent the wheel. It also means that we can study
flies, worms, yeast, mice, etc. and make important discoveries about humans.
This idea of conservation is very important, and most believe that it is
proof that evolutionary mechanisms are responsible for deriving the
biological life we see today. While this idea of conservation does not
prove evolution, and cannot disprove a designer creating organisms based
upon a common design, it is certaintly real.
The other issue is that if you look at something like a cell cycle gene or
genes with very essential function, they tend to have less sequence
divergence than signalling molecules or molecules that perform allosteric
interactions, etc. This plasticity of signalling molecules and stricter
conservation of essential genes is a very general phenomena. When Wells'
looks at a genes to show how incongruent the phylogenies are, he never makes
these important distinctions nor does he fairly portray the data. He simply
says look at how this one gene makes this tree of life sketch, whereas this
other gene does something completely different.
I think looking at the data more generally and open-mindedly argues strongly
for conservation of genes within organisms and will ultimately show that the
similarity we see among organisms by phenotype will be confirmed by
genotype. This is not surprising. The argument ultimately will be in how
to interpret this conservation of genetic function and how the phylogenetic
relationship was derived.
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