Donald Prothero detailed the history of interactions between creationists and biologists in his excellent commentary at skepticblog. Creationists always seemed to have the upper hand in populist debate, because they could claim - we just dont know what most of the DNA codes for, so we cant rule out that it has a function.” That ‘loophole’ was finally closed with Human genome sequencing.
But the most convincing evidence has come from our greatly improved understanding of entire DNA sequences, and what they consist of. Creationists play this game of we just dont know what most the DNA codes for, so we cant rule out that it has a function, but this has been a lie for decades. There are many different kind of DNA sequences that are clearly non-functional. These include: 1) pseudogenes, which look like they were once functional DNA, but have lost the ability to be expressed; 2) Transposons, or jumping genes, which can jump from one part of the DNA to another and yet are not expressed; 3) SINEs (short interspersed nucleic elements) and LINEs (long interspersed nucleic elements) which are segments of DNA stuck in the middle of a coding sequence that have no function or ability to code for proteins; 4) highly conserved non-coding non-essential DNA, which is very consistent in the sequences of many organisms suggesting that it is important, yet can be removed with no effect whatsoever (Westphal, 2004); and 5) repetitive DNA, which repeats the same sequence over and over again hundreds of times, and none of this repetitive genome seems to code for anything. Perhaps the most interesting and surprising of all of these junk sequences are endogenous retroviruses (ERVs). These are gene sequences of retroviruses that once infected us by inserting their DNA into our genome, but are no longer active. Instead, every time one of our cells divide we make new copies of this fossil DNA from a long-ago viral infection and carry it on through millions of generations. Clearly, these DNA fossils hiding in our genome no longer code for the virus, or for anything elsethey are clearly junk that we passively carry around with no ill effects. In the few cases where the retroviral DNA can be re-activated, it usually causes disease or other bad effects. Either way, it is of no comfort to creationists.
Creationists finally feel vindicated by ENCODE’s ‘discovery’ that 80% of the genome is functional as the linked article pointed out. That is not a bad thing for ENCODE’s continued US funding based on the following chart.