Over at his blog, Steve Matheson has been reviewing Stephen Meyer’s book, Signature in the Cell. Matheson quotes Meyer:
..the original DNA text in eukaryotic organisms has long sections of text called “introns” that do not (typically) encode proteins. Although these introns were once thought to be nonfunctional “junk DNA,” they are now known to play many important functional roles in the cell.
Here’s a short explanation for why Meyer’s statement is ludicrous. The human genome contains at least 190,000 introns (though it’s been recently estimated to contain almost 210,000). Together those introns comprise almost 1/4 of the human genome. One fourth. That’s 768 million base pairs. And biologists have identified “important functional roles” for a handful of them. How many? Oh, probably a dozen, but let’s be really generous. Let’s say that a hundred introns in the human genome are known to have “important functional roles.” Oh fine, let’s make it a thousand. Well, guys, that leaves at least 189,000 introns without function, and gosh, they’re snipped out of the transcripts and discarded before the darn things even leave the nucleus.
I would agree with Matheson that it is highly unlikely that a couple hundred thousand introns each have an “important functional role” “in the cell.” But I’d like to take the topic of introns and steer it into a much more interesting teleological direction.
Let me propose a hypothesis that flows naturally from the hypothesis of front-loading evolution: introns facilitated the evolution of metazoan life.
To this end, I have created the ‘introns’ tag and will be periodically exploring this hypothesis from several angles over the next few weeks/months.