11 February 2008

Talking trash about "junk DNA": lies about genomic research

In another post in this ongoing series, we looked at creationist distortions of the nature of research into non-coding DNA, or "junk DNA." There I mention how creationists of all stripes are quite fond of the claim that "Darwinist" assumptions led to the labeling of all non-coding DNA as non-functional, and thereby to the neglect of research in the field for three decades. I've been in biology for most of those 30 years, and I know this claim to be dishonest. But if you want to see for yourself, it's easy enough to determine whether the claim is true (or reasonable, at least). One way to check is to ask someone who actually knows the field (as opposed to, say, a lawyer or a former physicist). Another approach is to look at the evidence in the scientific literature. That's what I did, and here's how it went.

I used PubMed, the standard online (free) database of the biomedical literature, to search for various terms during different time frames. I limited the searches to articles written in English. In each graph, the vertical axis indicates number of unique scientific articles containing the phrase, and the horizontal axis indicates publication date, in five-year intervals. First, let's see how often we find the phrase 'junk DNA' and the related phrase 'selfish DNA.'

Things to notice about this graph:

  1. Neither phrase appears at all before 1970, and the phrase 'selfish DNA' doesn't appear till 1980.
  2. The use of both terms has steadily increased over time.
  3. The terms are extremely rare in the scientific literature. Total number of uses of 'junk DNA' in the past 40 years: 73.
Now, you might think this is pretty strong evidence in favor of the claim that the 'junk' assumption shut down research. Well, let's see. Ever heard of "satellite DNA?" That was an early term for a particular kind of non-coding DNA, composed of lots of small repeated sequences. Contrary to the dishonest claims of Ross and Co., satellite DNA was thought to be functionally relevant from its first description, and hypotheses regarding its roles were being vigorously tested before 1979. Folks, if all you did was read up on satellite DNA, you'd know enough to realize that neither RTB nor DI are telling you the truth about non-coding DNA. But let's see if it gets worse. (It does, of course.)

How much research has been focused on satellite DNA? Here's the graph:

If you look really hard you can see the little blue bars that show you the use of the term 'junk DNA.' And now you know why I am baffled as to why an honest person (much less a responsible Christian) would make a big deal out of the term 'junk DNA.' Biologists sure haven't. And now you know something else: research on satellite DNA was robust, and growing, throughout the 30 years following the first references to 'junk DNA.' Total number of papers that use the term: 4214. We could stop there. But we're just getting started.

You might have noticed that satellite DNA research seems to have peaked in the early 90's, and fallen off since. What's up with that? Heh. As methods for analysis of DNA and genomes improved, biologists recognized that satellite DNA could be categorized into two broad types: minisatellites and microsatellites. The technical differences don't concern us, but I think this graph will make it clear why the term 'satellite DNA' has become less prominent in the biomedical literature:
Got it? The new term was catching on, and replacing the old term. And what about microsatellites?

That's quite a different story, now isn't it?
Recapping so far – total numbers of articles, to date, using these phrases:

Junk DNA
Satellite DNA

What about introns? Those are the pieces of DNA interspersed in most genes (of organisms other than bacteria), pieces which are chopped out of the message before it's translated into protein. They're non-coding DNA, and therefore "junk" according to our creationist pundits. Question: how did research on introns fare during those 30 dark years of neglect?
Answer: pretty darn well. Total number of hits: 37,830.

Had enough? We could analyze research on ERVs, LINEs, SINEs, centromeres, telomeres... but I think it's clear enough that the fable about the evil Darwinists who killed an entire area of research, and with it countless victims of colon cancer and diabetes, is just a damned lie.

If you're just a Christian who's been reading this stuff, stop spreading the disease, and either give up the pointless opposition to common descent or find more respectable ways to defend your position.

If you're a Christian who's been writing this stuff, apologize, purge, re-orient, and maybe re-think. Your folk science is toxic, and our faith doesn't need "help" like that.


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