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:

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:

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-A^Uab-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}Ubx^HC148A element, so that two copies (P{(-FRT)lacZ.HP}Ubx^HC148A and P{(-FRT)lacZ.HP}abd-A^Uab-G1) are present in abd-A^Uab-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.