Commentary on the so-called Creation/Evolution/Intelligent Design Debate and Right-Wing nuttery in general - and please ignore the typos (I make lots!)

Monday, January 09, 2006

Similar 'shape' means similar DNA?

This is one of those all-too-common claims that we see when creationists are presented with evidence showing "similarity" in the DNA sequences for various creatures (e.g., humans and chimpanzees).
It has shown up again recently at the Telic Thoughts blog, written by one "Douglas":

No, IDists would say that a common designer will often use COMMON DESIGNS, and that similar structures will have similar DNA. Pretty simple.

Emphasis mine.

Such claims, in one form or another, pop up frequently in creation/evolution discussions. But does it make sense?
Superficially, yes.
Provided we are talking about genes and genomic loci that have an influence on morphology. How many such loci have been sequenced and compared? How many are even identified?
As far as I know, none. That is, I am unaware of any published study in which genes or other loci which are responsible for or influence basic body shape and structure* having been sequenced and compared between what evolutionists describe as related organisms, humans and chimpanzees or whales and hippos, for example.
So at best, the claim is an intuitive speculation, and it is probably correct at some level. Again, for genes producing morphology.
But I am unaware of any rational, scientific reason that would dictate that superficial morphological similarities between or among organisms will produce or require "similar DNA" sequences in genes that do not control of influence morphology. Which is to say most if not all published sequence comparions.

My own graduate and post-graduate research focuses on the molecular phylogeny of Primates. To examine these taxa, I used DNA sequences from the Beta Glogin gene cluster and the gene encoding serum albumin. Neither of these genes or gene families have a direct (or indirect, as far as I know) inluence on morphology. Yet phylogenetic analyses produce outcomes that are congruent with studies based on skeletal morphology and/or the use of other genetic loci.

Conclusion: The "similar shape equals similar DNA" retort of creationists/IDists is at best a cop-out.

*This does not include HOX and similar pattern-forming genes.

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