Re: [asa] How big a deal is homology?

On 3/28/07, David Opderbeck <dopderbeck@gmail.com> wrote:
>
>
> Don't get me wrong, I appreciated Collins' book and admire him, and I'm
> very glad he's injecting some new ideas into the coversation and that
> publications such as Christianity Today are taking notice. But, I still
> think his book was seriously weakened by some of his broader jabs at ID. In
> many cases, the TE pointing a finger at ID has three fingers pointing back
> at himself. At some point, given an orthodox understanding of God's
> sovereignty, it seems to me that the distinction between "progressive
> creation" and "creation by evolution" becomes meaningless.
>

So, given that theology is neutral to progressive creation vs. creation by
evolution, then the answer is determined what does the non-theological
evidence point to and for that it is abundantly on the latter. God COULD do
either. The question is what DID God do. Your concern about gene to
pseudogene transitions only deals with an edge condition of a larger issue
which is known as copy number variation. Copy number variation is where
parts of the genetic code get duplicated or deleted. The issues being
currently pondered look like this question: If particular genes have a
function then what is the "functional" difference when there exists copy
number variation? While copy number variation is getting lots of play these
days the idea has been around for quite a while. For example, during my
literature search I found a paper on it dating from 1987.This phenomonon
appears to make the genetic differences not only between between species but
within species larger than originally appreciated. The concept of genes as
"functional legos" that gets stacked differently from species to species by
the progressive creationists is thus overly simplistic.

For example,

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0020207

> Given that gene duplication is a major driving force of evolutionary
> change and the key mechanism underlying the emergence of new genes and
> biological processes, this study sought to use a novel genome-wide approach
> to identify genes that have undergone lineage-specific duplications or
> contractions [RDB note: these contractions are apparently what bothers
> David.] among several hominoid lineages. Interspecies cDNA array-based
> comparative genomic hybridization was used to individually compare copy
> number variation for 39,711 cDNAs, representing 29,619 human genes, across
> five hominoid species, including human. We identified 1,005 genes, either as
> isolated genes or in clusters positionally biased toward rearrangement-prone
> genomic regions, that produced relative hybridization signals unique to one
> or more of the hominoid lineages. Measured as a function of the evolutionary
> age of each lineage, genes showing copy number expansions were most
> pronounced in human (134) and include a number of genes thought to be
> involved in the structure and function of the brain. This work represents,
> to our knowledge, the first genome-wide gene-based survey of gene
> duplication across hominoid species. The genes identified here likely
> represent a significant majority of the major gene copy number changes that
> have occurred over the past 15 million years of human and great ape
> evolution and are likely to underlie some of the key phenotypic
> characteristics that distinguish these species.
>

See here for both positive and negative copy number variation amongst the
different great ape species:

http://biology.plosjournals.org/perlserv/?request=slideshow&type=figure&doi=10.1371/journal.pbio.0020207&id=9002

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Received on Wed Mar 28 11:42:17 2007