email - September 2011

Mole Thumb Response

John has a good point.

We encourage our readers to question us as much as we encourage them to question evolutionists. Thatís why we were glad to get this email from John regarding last monthís feature article.

In your article about the mole's 'thumb', you state, "To make things worse for evolutionists, other creatures closely related to the mole donít have this kind of ďthumbĒ because they donít have the gene for it."

I'm not sure that statement is actually backed up by the quote you provide.† All the quote actually said was, "The gene product was absent from this region in the shrew."

They may be saying that the gene did exist in the shrew genome, just that it wasn't expressed in the wrist bone.† A quick Google search for "gene msx2" took me to this page, http://www.genecards.org/cgi-bin/carddisp.pl?gene=MSX2, which I don't understand much but I recognise the words 'drosophila' and 'human', which seems to imply that this gene (or something like it) is in both fruit flies and humans, so I'm guessing it's in most eukaryotic life including the shrew.

From that perspective, the new thumb may not require any new gene to have appeared, merely a gene duplication event, or perhaps some change in the non-coding DNA surrounding it, that would cause it to be expressed differently (as seems to have happened in the origin of lactase persistence).† This would not be nearly as improbable as the origin of a new gene, which is how you seem to have interpreted the quote, which I agree would be practically impossible.

There are certainly powerful arguments against evolution being able to produce genes that encode for proteins with different folds to those that previously existed in the genome, and hence being able to generate all life.† But let's not underestimate what may be within the bounds of microevolution, the different uses of existing genes.† Given the quote you present, I think the panda/mole's thumb could have come about by microevolution (though, as you say, that doesn't prove that's how it happened.)

Yes, John has a good point.† I should have been more precise.

The MSX2 gene page he referenced says the gene "Acts as a transcriptional regulator in bone development."† Therefore, one would expect it to be present in any creature with bones. † It's presence in a certain region of the mole genome causes a bone to grow a "thumb" out of the mole's wrist.† Since it is absent in that region of the shrew's genome, the shrew does not grow that bone.

It would be nice if there were a one-to-one correspondence between genes and physical features, but, in practice it seems more complicated than that.† One gene is often predominately associated with a physical feature, but there is usually more to it than that.† Genes seem to work in combination to produce some physical features, and some genes seem to play more than one role in different situations.

So, John is right.† I did oversimplify when I wrote that shrews "don't have the gene for it."† But it is hard to have any discussion of genetics without a certain amount of simplification.† Looking back over the previous paragraph I said, "Genes seem to work in combination ...".† Strictly speaking, genes don't really "work" themselves.† They contain the instructions telling other biological processes how to work.

The more precise language becomes, the more difficult it is to understand (as anyone who has ever tried to read a legal contract knows).† It is difficult to convey complex ideas in simple terms.† I'll try to do better in the future.

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