A quote from an extremely mediocre book, Complexity: A Guided Tour. Like most people coming out of the 'complexity sciences', the author has a mediocre grasp of molecular biology, both current developments, and the history of the field. It's frustrating that these network people keep hyping supposedly new revolutionary discoveries made the past 10 years of the genome era - discoveries, that in fact have been known for decades. For people clearly new to biology, molecular biology before the year 2000 was a big black hole of ignorance.

There are several claims that make me angry in this book, but here's one claim that is like a zombie and refuses to die, no matter how many times it's been knocked down:

Proponents of Evo-Devo propose that morphological diversity among species is, for the most part, not due to differences in genes but in genetic switches that are used to turn genes on and off. These switches are sequences of DNA - often several hundred base paris in length - that do not code for any protein. Rather they are part of what used to be called "junk DNA," but now have been found to be used in gene regulation...

And then there's this excruciating passage:

According to Evo-Devo, such modifications - in the parts of DNA long thought of as "junk" - are the major force in evolution, rather than the appearance of new genes. Biologist John Mattick goes so far as to say, "The irony... is that what was dismissed as junk [DNA] because it wasn't understood will turn out to hold the secret of human complexity.

OK class, let's go over a little history:

1972: The term 'junk DNA' is coined. It is not used to refer generally to non-coding DNA.

1967: Mark Ptashne shows that a regulatory transcription factor (the lambda phage repressor) binds to non-coding DNA flanking the protein-coding genes.

And the idea that genes are regulated by non-coding sequences was around well before that. Certainly long before Evo-Devo came on the scene.




Second, John Mattick is clueless, and he should not be quoted. So junk DNA holds the secret to human complexity? Then I supposed it also holds the secret to the incredible complexity of an onion, which has five times more non-coding DNA than humans. Ryan Gregory came up with the onion test to counter the nonsense peddled about junk DNA:

The onion test is a simple reality check for anyone who thinks they have come up with a universal function for non-coding DNA1. Whatever your proposed function, ask yourself this question: Can I explain why an onion needs about five times more non-coding DNA for this function than a human?

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