evidence of common descent from It's the Bible or evolution

From: Dr. David Campbell <amblema@bama.ua.edu>
Date: Thu Oct 06 2005 - 11:32:17 EDT

There are two reasons why gene similarities, such as pseudogene
duplication, provide evidence of common descent.

First, although examples of random convergence or convergent evolution
exist, an overwhelming level of similarity is present in most
comparisons. Furthermore, there are statistical tests that can help
assess whether the similarity is greater than expected by chance. It
is true that the existence of random similarities lowers the
significance of any one similarity as evidence for common descent.
However, it is not logical to therefore dismiss all genetic similarity
as random. It may also be worth noting that denying the ability to
distinguish between significant pattern and chance similarity rules out

Secondly, these similarities often have no functional significance that
can be determined. There's no evident reason to design things that way
if the genomes of the different organisms were created separately.
This does not prove that a designer could have had some unknown purpose
in doing that, much less that a designer could not have designed
without creating separately. However, the match with evolutionary
expectations is excellent.

A complicating factor is that there are often evolutionary reasons for
genetic similarities to potentially be misleading. Overlooked effects
of paralogous genes, differential preservation of multiple ancestral
alleles, convergent evolution, long branch attraction, and other
factors complicate the matter. Although it's true that the range of
possible outcomes compatible with an evolutionary explanation makes any
one outcome a weaker confirmation, this is logically invalid as
evidence against evolution.

Dr. David Campbell
425 Scientific Collections Building
Department of Biological Sciences
Biodiversity and Systematics
University of Alabama, Box 870345
Tuscaloosa AL 35487-0345  USA
Received on Thu Oct 6 11:34:05 2005

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