Darwin's proof, chapter 5, part II

I am continuing my review of chapter 5 of CG Hunter's Darwin's Proof. The mistakes are very dense in this part, so discussing only six pages of his book will require a lot of ink.

Hunter next deals with the evidence from genomic comparisons. He first tries his hand at the fact that humans and chimpanzees have 98.7% of our DNA in common. First, he says that this difference is too small to account for the difference between humans and chimps. Of course it can account for it. That has nothing to do with evolution. However humans and chimps differ, it is encoded in our DNA. However much our DNA differs, whether it is 99% or 50%, that accounts for how we differ, for creationists as well as evolutionists. Hunter seems to be denying that DNA actually determines the characteristics of humans and chimps. What does he suggest does account for our differences, if not our DNA? He points out that humans and mice have almost nearly 98% of our genes in common, just like humans and chimps, but here he is subtly switching comparisons. With the human mouse comparison he is simply comparing how many of our genes have an ortholog in mice. He is not comparing how similar those genes are, which is what is being compared in humans and chimps. When we do that comparison, mice and humans are 91.3% similar.

He then points out that evolution doesn't predict 98.7% similarity. Of course it doesn't. He is right that it could be 99% or it could be 80%. No one claimed evolution predicted that number a priori. The number isn't evidence for evolution. The significance of the number is that a relatively small difference in DNA can account for dramatic differences in the organisms; it was never given as evidence for evolution directly. The evidence is found in the pattern of similarities when we compare the DNA of many organisms, and their correlation with other characteristics. The high number just reminds us that we are not as unique as we think--in fact it is similar to the difference between a horse and a donkey (99%).

Next Hunter tackles what I think is wonderful evidence for evolution, the fact that coding regions are more similar between species than noncoding regions. This happens because the noncoding regions are unconstrained and selection will not remove mutations, but most mutations in coding regions are removed by selection. How does he address this? He points out that it can be explained by evolution only if the noncoding regions are nonfunctional, so that is an assumption we are making. No, it isn't. It has been tested. Certainly the fact that the third base of a codon is usually redundant is testable. The fact that pseudogenes aren't transcribed is testable. The fact that introns are degraded after excision and dramatic changes in their sequence has no effect is testable.

Then Hunter tries his usual gambit--he says evolution would have no problem if we didn't see that pattern, or any possible pattern. If we saw something different, we would just assume that the region that didn't change must have a function. No we wouldn't. We would assume that, based on evolutionary theory, but would have to find the function. If a conserved region was observed and we could not find a function, it would be unexplained by evolution. As it is, the opposite is true. Every time we find a conserved region, we soon find a function. It is a great way to identify importan cis regulatory elements, for example.

The next topic Hunter addresses are examples of small scale evolution, like the beaks of the finch or the peppered moth. He admits we have seen these, but says that these changes appears to have limits. He says this several times in various ways, but never cites any evidence at all that there are such limits. I would love to find them. In fact, I give students in any of my classes an outomatic A if they can find any evidence for such a limit. Hunter ignores the vast literature comparing the changes in the fossil record with observed changes. This literature has shown that the kinds and rates of changes that we see today are consistent with the changes in the fossil record. Hunter claims that small scale changes do not appear to be able to extrapolate to large changes when in fact the literature shows just the opposite.

Hunter quotes mines Ernst Mayr saying we don't know how genotype changes bring about the changes in phenotype. Mayr was pointing out that we didn't know exactly how genetic changes bring obout phenotypic changes. That is being very well addressed today by the field of evo devo, which is in fact filling in this last gap in our knowledge and showing how specific DNA changes lead to specific phenotypes. But even without these advances, this is at best an argument from ignorance.

Then Hunter moves the goal posts and points out that small scale evolution requires a reproductive apparatus in the first place, so how did that come about, huh?

Hunter's last section is on the origin of life. Yes, he has a section on the origin of life in the chapter on evidence for evolution. When has the origin of life ever been presented as evidence for evolution, rather than a question for evolution? Every biologists knows there is a lot we don't know about the origin of life. It is an unanswered question. No one has ever brought it up as positive evidence for evolution. Hunter already had two chapters on problems with evolution, and it would make more sense to put the origin of life there. In fact, he did. He just felt like bringing it up again here because he really likes the areas where we are less certain and he really likes to get back to ultimate origins as often as he can.

Hunter doesn't even try in these chapters to address several other kinds of evidence, such as development or biogeography. In fact, I have never seen anyone deal with biogeography. Overall, his attack on the positive evidence is very feeble. He mostly grants the evidence, but then declares it unconvincing or ambiguous. Never does he hint at the true depths of evidnece or go into any detail.