Shoddy But Not "Junk"?

Philip Ball is a freelance science writer based in London (UK). He frequently writes for Nature. His latest article is a review of a recently published paper by John Avise [What a shoddy piece of work is man]. Apparently Avise has just published a paper in PNAS where he points out that our genome does not look like it was designed. It's an attack on Intelligent Design Creationism and Adaptationism.

I can't find the paper but I have read Avise's book, Inside the Human Genome so I'm familiar with his thesis—and I agree with it.

The purpose of this posting is not to review the points that John Avise makes but to comment on one of the points made by Philip Ball. At the end of his Nature review he says,

However — although heaven forbid that this should seem to let ID off the hook — it is worth pointing out that some of the genomic inefficiencies Avise lists are still imperfectly understood. We should be cautious about writing them off as 'flaws', lest we make the same mistake evident in the labelling as 'junk DNA' genomic material that seems increasingly to play a biological role. There seems little prospect that the genome will ever emerge as a paragon of good engineering, but we shouldn't too quickly derogate that which we do not yet understand.

THEME

Genomes & Junk DNA

I just gave a talk on junk DNA where I explained to my audience the nature of the scientific controversy. We know for a fact that our genome is littered with pseudogenes of all sorts and we know for a fact that more than 50% of our genome is repetitive DNA of one kind or another. A good hunk of that is degenerative transposons and fragements of transposons [Junk in your Genome: LINEs]. Another large hunk is Alu sequences: fragments of an ancient primate transposon derived from 7SL RNA [Transcription of the 7SL Gene].

We also know a great deal about introns and that knowledge leads to the conclusion that most intron sequences are dispensable. it's part of the junk in our genome. We know about the genetic load argument [Genetic Load, Neutral Theory, and Junk DNA] and we know about the C-Value Paradox. Most scientists who study the problem of junk DNA know about The Onion Test.

My point is that it's extremely misleading to suggest that our identification of junk DNA is based on a lack of understanding. That's simply not true. There are some very good scientific reasons for maintaining that most of our DNA is junk based on over 40 years of work on genome organization.

Yes, it's true that there have been some scientific challenges questioning the conclusion of those studies. There is a group of scientists who claim that vast amounts of our genome serve some mysterious purpose that's only vaguely defined. It could be regulation of some sort or even an entire new class of RNA-encoding genes that make us human.

These claims make the debate over junk DNA a scientific controversy but they certainly haven't succeeded in disproving the hypothesis. None of the recent claimants can explain pseudogenes and degenerative transposons, which make up more than half of our genome. None of the opponents can refute the genetic load argument.

Science writers like Philip Ball can be forgiven for not delving into the problem. It's easy to fall for the latest articles that purport to show function for a large part of what we call junk DNA. After all, those anti-junk proponents don't do their homework either and they gloss over all the data that contradicts their "new" hypothesis.

My point is that the idea of junk DNA is alive and well in spite of what modern science writers seem to think. It's just not true that today's scientists think we made a big mistake in the past by calling it junk DNA. This is still very much a scientific controversy and it's too soon to tell how it will pan out.

Personally, I think the evidence in favor of a large amount of junk in our genome is persuasive and I'd be very, very surprised if a significant amount of it turns out to be functional. I wish science writers would stop behaving as though the issue had been resolved and junk DNA is dead.

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