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Friday, September 07, 2007

Dogs and more dogs - More on why dog breeding is not a model for evolution

Recently, I featured comments on Richard Dawkins's (possible non-) review of Michael Behe's Edge of Evolution for the New York Times - in which Dawkins tried to evade bad news for Darwin's theory by appealing to human dog breeding.

In that post, I featured comments from Dr. David DeWitt, who pointed out that dog breeders select animals for juvenile canine traits that people happen to admire.

(Most people prefer to live with a happy puppy rather than the Big Bad Wolf.)

But that has nothing to do with survival in nature and does not confer or lead to new traits in canines. So, contrary to Dawkins's claims, it cannot be used as direct evidence for Darwin's theory.

(No one doubts that all sorts of changes may be possible - in theory. But which changes play a role in the development of life forms in nature itself? The weird choices of dog breeders hardly count there.)

After I posted that item, some correspondence followed from friends in science. I am posting some of it here, with permission:

One friend, who works in a lab, writes,
... many biologists use the mouse as a model organism of choice, and we use particular inbred strains.

Like inbred dogs, they are dumber and more prone to particular types of tumors/defects, so while they are more homogeneous in behavior from mouse to mouse, they are also just less fit.

I bring them up because like the observed experiments on E. Coli [ in Edge of Evolution], we are treating these organisms as relatively static. When I order a C57Bl/6 mouse from Japan, I don't worry that reproductive isolation has produced one that is different from the one here in Maryland.

And when we introduce mutations in mice, we don't assume that they'll evolve and improve upon them. If those genetic alterations were to disappear in a generation (which is only ~3 months in mice), people would make much note of it. But mouse colonies in research institutes throughout the world are telling us that this does not occur.


Does that mean that lab mice can never change? No! He adds,
it has been reported that sometime prior to 1984, a mutation did develop in the C57Bl/6 strain:
"A naturally occurring deletion in nicotinamide nucleotide transhydrogenase (Nnt) exons 7-11 occurred in C57BL/6J sometime prior to 1984. This deletion results in the absence of the NNT protein, and is associated with impaired glucose homeostasis control and reduced insulin secretion. This mutation is not found in C57BL/6JEi, C57BL/6N, C57BL/6ByJ, C57BL/10J, C57L/J, or C58/J (Toye AA, et al, Diabetologia, 2005)."

So the mutation was a health problem for the mouse.

Another friend writes to say that the dog genome has not been affected in any signfiiant way by Darwinian changes:
Following talk about dogs by Dawkins, there has appeared an excellent article about the dog genome in American Scientist (September-October 2007): Genetics and the shape of dogs by Elaine A Ostrander (National Human Genome Institute of the NIH). This details much of the research on the dog genome by her and her team and others in the field.

It is well written with excellent illustrations. It appears that most of the variations between breeds of dog are incipient in the dog genome with little due to recent mutations. I think this was already known but this article deals with it in an authoritative way. I hope Dawkins reads it!

You hope Dawkins reads it? But wasn't the whole point of his review to discourage people from reading Mike Behe's Edge of Evolution? Just today I was talking to a science teacher who had started to read it - and was not slow to recognize the devastating attack on ultra-Darwinism that it represents.

Also, another friend writes: Following talk about dogs by Dawkins, there has appeared an excellent article about the dog genome in American Scientist (September-October 2007): Genetics and the shape of dogs by Elaine A Ostrander (National Human Genome Institute of the NIH). This details much of the research on the dog genome by her and her team and others in the field.

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