A discussion about junk DNA has broken out in the comments to Monday's Molecule #128: Winners.
Charlie Wagner, an old talk.origins fan, wonders why junk DNA advocates are still around given that there have been several recent papers questioning the idea that most of our genome is junk.
Charlie asks ...
So why are Larry and many others still clinging to the myth of "junk DNA"? Do they not read the literature?Of course we read the literature, Charlie, but unlike you we read all of the literature. You can't just pick out the papers that support your position and assume that the question has been settled.
The skill in reading the scientific literature is to put things into perspective and maintain a certain degree of skepticism. It's just not true that everything published in scientific journals is correct. An important part of science is challenging the consensus and many scientists try to make their reputation by coming up with interpretations that break new ground. The success of science depends on the few that are correct but let's not forget that most of them turn out to be wrong.
Genomes & Junk DNA
The trick is to recognize the new ideas that may be on to something and ignore those that aren't. This isn't easy but experienced scientists have a pretty good track record. Inexperienced scientists may not be able to distinguish between legitimate challenges to dogma and ones that are frivolous. The problem is even more severe for non-scientists and journalists. They are much more likely to be sucked in by the claims in the latest paper—especially if it's published in a high profile journal.
Lots of scientists don't like the idea of junk DNA because it doesn't fit into their view of how evolution works. They gleefully announce the demise of junk DNA whenever another little bit of noncoding DNA is discovered to have a function. They also attach undue significance to recent studies showing that a large part of mammalian genomes are transcribed at one time or another in spite of the fact that this phenomenon has been known for decades and is perfectly consistent with what we know about spurious transcription.
I've addressed many of the specific papers in previous postings. You can review my previous postings by clicking on the Theme Box URL. The bottom line is "don't trust everything you read in the recent scientific literature."
Another good rule of thumb is never trust any paper that doesn't give you a fair and accurate summary of the "dogma" they are opposing. When you challenge the concept of junk DNA, for example, it's not good enough to just present a piece of new evidence that may not fit the current "dogma." You also have to deal with all the evidence that was used to create the consensus view in the first place and show how it can be better explained by your new model. A good place to start is The Onion Test.
The figure is from Mattick (2007), an excellent example of what I'm talking about. This is a paper attacking the current consensus on junk DNA but in doing so it uses a figure that reveals an astonishing lack of understanding of genomes. This makes everything else in paper suspect. The figure was chosen by Ryan Gregory to be the classic example of a Dog's Ass Plot.
Mattick, J.S. (2004) The hidden genetic program of complex organisms. Sci Am. 291:60-67.