Since I haven't read the book I won't comment on it much , other than to say it sounds very similar to some other arguments I've heard before, and I don't think it's valid.

Since the science seems to be missing in this thread, I'll offer a little primer on introns, for those that are interested. If you only learn one thing here, about introns or otherwise, I'll be happy.

DNA is composed to two main classes: coding regions and non-coding regions. Introns are in a subclass of coding regions - but first, lets define the (much more straight forward) coding regions.

Coding regions are composed of exons, and exons encode genes, and these are sequences of DNA that make protein. Lots of people forget this, or misunderstand it, and it's important. Genes encode protein. Protein includes "structural" protein, like the keratin in your hair, and also lots of little molecular machines that make and break stuff. They aren't magic wands that bequeath speech - there are a whole bunch of genes necessary for this, and not all of them are known. There is a middle man here called RNA - I'll get to that later.

Non-coding DNA includes stuff like strucutural DNA, that proteins can bind to, so your chromosomes stay in tact.

It also encodes regulatory DNA called "promoters". Promoters are sequences of DNA that tell the cells how much protein to make, and when. Not all genes are "on" all the time. You can think of promoters as sort of a dimmer switch for a light - on, off, and a bunch in between. Different cells, at different times, make different proteins.

Introns are short sequences of DNA found in between exons. Before making a protein, the DNA sequence of a gene is read by some of those little protein machines I mentioned earlier, and a RNA strand is made. The RNA initially contains both introns and exons. Then, the introns in the RNA are "spliced out" or removed by more protein machines. Then, more protein machines "read" the RNA, and make a protein.

Why there was this apparently useless DNA that just got removed was baffling to scientists initially, hence the name "junk DNA". It is no longer thought of as junk; several functions for introns are now known - I'll give you a couple. It wouldn't surprise me if even more is discovered later.

1. Alternative splicing: Sometimes, a gene will be spliced differently under different circumstances. In cell A, there might be three introns spliced out, and in cell B, there might only be two, but one of them is slightly bigger. Now there are two very similar, but slightly different proteins in different cells - and there has been an "economy of DNA" - only one gene! Cool, huh?

2. Introns are regulatory elements. This works in a couple of different ways - sometimes, an intron ban act like a promoter, or with a promoter, to turn a gene on or off. Sometimes, the intron can affect RNA stabilty, so the amount of RNA that gets made into protein can be affected.

There is a famous quote by a scientist (sorry, I forget who) said something like "Give me the regulatory elements of a man and the genes of a man, and I'll give you a man; give me the regulatory elements of a mouse and the genes of a man and I'll give you a mouse." I forget who said it. Anyway, at the time everyone thought he was nuts, but this is now (at least partially) accepted.

Of course, all this fuss about introns really has nothing to do with the validity of the argument, in my opinion. If you have questions about homologs and orthologs of genes, mutation rates, and selective pressures, let me know... I think these are more relevent.