Pharyngula

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A creationist, Rob McEwen, left me a little comment here which lists a number of his objections to evolution. It?s a classic example of the genre, and well illustrates the problem we have. The poor fellow has been grossly misinformed, but is utterly convinced that he has the truth. I?m not going to dismantle his entire line of blather (thanks to Loren Petrich, who has already briefly pointed out the flaws in his thinking), but I do want to show what I mean with one example.

Here?s what Mr McEwen says:

Mutations have NEVER produced additional DNA structures. NEVER! Even as scientists study mutations in fruit flies or viruses? the mutations sometime just scramble existing DNA? but MORE OFTEN, they DELETE DNA structures. Certainly, ?survival of the fittest? is a means by which nature purges the gene pool of bad mutations, but NO evolution occurs here. (This alone is a DEATH BLOW to Evolution.) I repeat? not a SINGLE scientist in the entire world has EVER recorded a mutation which produced additional DNA structures or material…. but DELETIONS are recorded ALL THE TIME!!!

Wow. He certainly is emphatic, isn?t he?

And here?s the scary thing: for all his certainty, which he almost certainly got from common sources in the creationist literature, he is absurdly, absolutely, trivially, unforgivably wrong.  That paragraph is one solid block of lies. This is what biologists have to deal with all the time, people who rant falsehoods, either out of maliciousness or simple purblind ignorance, and the mobs of people who gullibly believe them.

The truth is that many kinds of mutations very commonly produce additional DNA structures. One very common and frequently observed method is unequal crossing over. Anyone with a little background in genetics or cell biology will be familiar with the idea of crossing over: during meiosis, homologous chromosomes line up side by side, and swap bits of their DNA at points of contact called chiasmata. Here?s what they look like:

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Normally, crossing over occurs between homologous regions of DNA, so there is no net gain or loss of DNA in either chromosome. However, it can occur by error between nonhomologous regions. When that happens, you do get a loss of DNA in one chromosome, and a gain in the other. Take a look at this diagram, which illustrates what goes on in an unequal crossing over event:

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As you can see, the end result is that chromosome number 2 has suffered a deletion and has no copies of gene C, while chromosome 3 has gained an extra copy of gene C. Quite contrary to Mr McEwen, every unequal crossing over event produces an equal number of gametes bearing duplications and deletions. If gene C is essential, however, the gamete bearing a deletion is unlikely to be viable, while the duplication may have no or little effect; in viable progeny, therefore, you are more likely to see duplications than deletions.

There are also additional well-documented mechanisms that can produce additional DNA, such as insertions and translocations. People design experiments all the time that make use of duplications. We can sequence the relevant region of the chromosome and explicitly identify duplicated stretches of DNA. You can open up catalogs of mutations and find long lists of lines that carry identified duplications; you can even send a little money to a stock center and they?ll send you back flies or fish or mice that carry such mutations.

I went to the Flybase database, for instance, and did a search for any duplicated alleles. It came back with a long list of them, and here is just the first one, an allele called abd-AUab-G1, which happens to be a Hox gene in the bithorax complex. Here?s the short description.

Head to head duplication of the starting P{(-FRT)lacZ.HP}UbxHC148A element, so that two copies (P{(-FRT)lacZ.HP}UbxHC148A and P{(-FRT)lacZ.HP}abd-AUab-G1) are present in abd-AUab-G1. (Bender and Fitzgerald, 2002)

You want the full citation so you can go look up the details in the peer-reviewed scientific literature? Yeah, we can do that:

Bender and Fitzgerald (2002) Transcription activates repressed domains in the Drosophila bithorax complex. Development 129(21): 4923-4930.

Let me remind you what Mr McEwen claimed. ?Mutations have NEVER produced additional DNA structures. NEVER!? Well, that?s certainly not true, is it? How about his claim that ?not a SINGLE scientist in the entire world has EVER recorded a mutation which produced additional DNA structures or material?? I think I certainly have shown that scientists have recorded such things. Want a few thousand more? I wonder if Mr McEwen even realizes that when he says such things to a scientist, the first thing that pops into their heads is a plethora of counter-examples and trivial mechanisms that trivially refute all of his points without even a moment?s hesitation…

I wouldn?t be at all surprised to learn that Mr McEwen is a decent, sincere person in addition to being a fervent believer in his religious dogma. However, he has been consistently misled. His sources have lied to him. And he is working hard to propagate those same lies to more people. That?s the real tragedy of creationism, that it is a fabric of outright dishonesty that persuades good people to do wrong, all in the name of their religion.

Comments

  1. #1 Torbjörn Larsson
    March 28, 2007

    Weren’t copy number variations found to be rather common in humans? Which makes McEwen even funnier.

    Molly, CalGeorge:

    You are essentially right, but as in all walks of life there are a few oddballs or nuts. Some professed atheists are creationists, and DI loves to point them out.

    A blog example is “charlie wagner” (not to confuse with Charlie Wagner commenting at times), now banned from Pharyngula and The Panda’s Thumb due to misbehaving. It is believed by some that he is “realpc” now trolling the later blog. He is easy to find, and you may enjoy watching him distort threads.

  2. #2 Torbjörn Larsson
    March 28, 2007

    is this “realpc” guy really a creationist

    Glen made an excellent description. I especially liked “He’s not trolling just to be an ass, he’s trolling because he doesn’t know how not to be an ass.”

    If “realpc” is “charlie wagner”, the later has sometimes looked like a stealth creationist. But the one time I called it on him he had plausible deniability. :-)

    Anyone who is married eventually rids themself of this idea of ‘winning’ an argument.

    I hear that some married men speculate that arguments are used primarily for socializing. Quaint – and wasn’t this why blogs were invented anyway?

    Bill:

    lumping all Creationists under the same definition.

    Oh, the definition for a creationist is that he/she believes in creation events. And since all creationists behave the same we can usually conflate their arguments.

    For example, as McEwen you don’t explain why information is important in a basic theory of biology. (Or even define it.)

    And as all creationists, you don’t see that the answers to most of your questions is accessible. In your case, in this thread even, see for example comment #29. You would seem more lucid if you tried to follow the actual arguments and commented accordingly.

    Meanwhile, evolution observes and explains observable characters of life.

  3. #3 David Marjanovi?
    March 29, 2007

    Amplification of genes leading to resistance of tumor cells against chemotherapy is an obvious example of a relevant mechanism. It is not real evolution

    Why not? Descent with modification by mutation, selection and drift — that fits precisely, doesn’t it?

    So both DNA & RNA would have to evolve at roughly the same time to be of any use….But yet neither can exist without the other! A chicken and egg Scenario!!

    Wrong. One word for you: ribozyme.

  4. #4 David Marjanovi?
    March 29, 2007

    Amplification of genes leading to resistance of tumor cells against chemotherapy is an obvious example of a relevant mechanism. It is not real evolution

    Why not? Descent with modification by mutation, selection and drift — that fits precisely, doesn’t it?

    So both DNA & RNA would have to evolve at roughly the same time to be of any use….But yet neither can exist without the other! A chicken and egg Scenario!!

    Wrong. One word for you: ribozyme.