As I've been saying for some time, the fact that we only understood the function of 10% of the Genome did NOT mean that the other 90% was random junk that had grown to fill the "spare" space.

The effort of holding and copying long DNA codes is considerable, so there is an evolutionary imperative to shorten DNA and clip junk. (Experiments in closed-chamber evolution of microbes have shown that if you supply a wide range of biological molecules that are normally manufactured inside the cell, then the organism will evolve and discard the unneeded DNA that codes for the enzymes that make those molecules)

http://www.theage.com.au/news/in-depth/you-and-your-dna/2007/07/28/1185339312711.html

Scientists thought they had started to get a handle on the human genetic code, but recent discoveries that "junk" DNA is in fact vitally important has sent biologists back to the drawing board, writes Roger Highfield.

SEVEN years ago, with much ballyhoo, scientists unveiled the book of life — the DNA required to build and run a human being. Recently, a small army of geneticists reported the results of the first systematic attempt to make sense of this book.

What they found makes uncomfortable reading for those who thought they understood the basics of biology, but it does provide tantalising hints of new ways to fight disease.

This, the most detailed study of DNA to date, is a landmark in genetics research, for the more scientists understand the details of how our bodies work, the easier it will be to fix them when they go wrong. But the latest findings turn basic biology concepts upside down, could rewrite conventional wisdom when it comes to common ailments, and contain many puzzles, including one that may even challenge our understanding of the way evolution works.