"Faith and the Human Genome", by Dr. Francis Collins

[T_aquaticus]

I have mentioned the essay “Faith and the Human Genome” by Dr. Francis Collins in various threads, and I thought it might be helpful to highlight it again in a thread of its own. Some questions about the legitimacy of both the theology and science of theistic evolution and evolutionary creationism have been bouncing around these forums and the interwebs. I think Collins’ essay does a great job of addressing both. It is both his personal testimony and a general description of his theological views as they apply to biology, evolution, and life’s history.

Essay found here:

PSCF9-03Collins.pdf

Collins lists several pieces of evidence for common ancestry and evolution, one of which is the differing rates of sequence divergence between exons and introns. I haven’t seen this argument used very often in forums or discussions like these, so I thought I would mention it. From the essay:

Eric Green at the Genome Institute has looked at this same region in many other species and, in fact, you can find this same CAPZA2 gene in everything from chimps down to zebra fishes and a lot of things in between (see Figure 4). Notice the pattern. The chimpanzee is almost 100% identical to the human, except the chimp has a deletion just before exon 2 that we do not have. Otherwise the match-up, as in most cases of human and chimp comparison, is about 98.5% to 99%. You can see that the baboon is starting to diverge. The cat and the dog and the cow all look a lot alike, and again if you look at the CAPZA2 exons, you will see that every one of those species has a nice conserved little segment there. But as you get further away to rats, mouse, chicken, two different kinds of pufferfish and then a zebra fish, about the only thing you see is the protein encoding regions, while the rest of the scattered noise goes away. Again, this is a very compelling kind of pattern in terms of what one would expect from evolution.

What is cool about this piece of evidence is that you can check it out for yourself at the UCSC Genome Browser found here: UCSC Genome Browser Gateway

Just type in the CAPZA2 into the Position/Search term, click on the first hit, and it will show you the gene in the human genome along with the sequence conservation across several model vertebrate species and the overall sequence conservation across 100 vertebrate genomes (“Cons 100 Verts”). In fact, you can do this across the entire human genome. Here is a snapshot I took of CAPZA2 from the UCSC genome browser:

I have never seen creationists try to explain this pattern. Why would the introns differ more than the exons when looking at homologous genes across vertebrate species? Why does similarity in introns correlate with the proposed evolutionary distance?