Thoughts in a Haystack

Oh, my goodness!

The Discovery Institute's attack chihuahua, Casey Luskin, is actually taking a page out of Answers in Genesis' (and about every other young-Earth creationist organization's) book. It is the ol' "we are using the same evidence but just interpret it from different starting points" ploy.

In responding to what Luskin characterizes as Ken Miller's argument that evidence for common descent refutes Michael Behe's "irreducible complexity" claims, Luskin says:

[A] piece of evidence Dr. [Kenneth] Miller commonly cites as demonstrating human/chimp common ancestry is the fusion of chromosome 2 in humans, which he argues has a structure similar to what one would expect if chimp chromosomes 2a and 2b were fused together, end to end. Without belaboring the details (which are covered elsewhere), the evidence for human chromosomal fusion simply indicates that our ancestors once had 48 chromosomes. But it tells us nothing definitive about whether our lineage leads back to a common ancestor shared with with apes. Human chromosomal fusion merely shows that at some point within our human lineage, two chromosomes became fused. That's it.

If we step outside the Darwinian box, then the following scenario becomes possible: (1) The human lineage arose separately from that of apes with 48 chromosmes, (2) a chromosomal-fusion event occurred, and (3) the trait spread throughout the human population. In such a scenario, the evidence would appear precisely as we find it, without any common ancestry between humans and apes. The two diagrams at right show two models for explaining the evidence for human chromosomal fusion.

At most, the fusion evidence confirms something we already knew: humans and apes share a similar genetic structure. But this might have been predicted by morphological studies without considering evolution. Again, common design can also account for such functional genetic similarities, and the fusion evidence does not demonstrate that humans share a common ancestor with apes.

Dr. Miller may reply that his model predicts the fusion evidence. But if we didn't find evidence for fusion in human chromosome 2, would that really refute Darwinism? No. Evolutionists would just claim that the fused telomeres and extra centromere were deleted. Miller assumes that functional genetic similarities must result from common descent, ignoring the possibility that such biochemical similarities might result from common design upon a functional blueprint.

Luskin even produces a diagram to "illustrate" his point:


First, let's get Miller's argument from his own mouth, rather than as spun by Luskin and the other IDers:

We've known for a long time that we humans share common ancestry with the other great apes—gorillas, orangs, chimps, and bonobos. But there's an interesting problem here. We humans have 46 chromosomes; all the other great apes have 48. In a sense, we're missing a pair of chromosomes, two chromosomes. How did that happen?

Well, is it possible that in the line that led to us, a pair of chromosomes was simply lost, dropping us from 24 pairs to 23? Well, the answer to that is no. The loss of both members of a pair would actually be fatal in any primate. There is only one possibility, and that is that two chromosomes that were separate became fused to form a single chromosome. If that happened, it would drop us from 24 pairs to 23, and it would explain the data.

Here's the interesting point, and this is why evolution is a science. That possibility is testable. If we indeed were formed that way, then somewhere in our genome there has to be a chromosome that was formed by the fusion of two other chromosomes. Now, how would we find that? It's easier than you might think.

Every chromosome has a special DNA sequence at both ends called the telomere sequence. Near the middle it has another special sequence called the centromere. If one of our chromosomes was formed by the fusion of two ancestral chromosomes, what we should be able to see is that we possess a chromosome in which telomere DNA is found in the center where it actually doesn't belong, and that the chromosome has two centromeres. So all we have to do is to look at our own genome, look at our own DNA, and see, do we have a chromosome that fits these features?

We do. It's human chromosome number 2, and the evidence is unmistakable. We have two centromeres, we have telomere DNA near the center, and the genes even line up corresponding to primate chromosome numbers 12 and 13.

Is there any way that intelligent design or special creation could explain why we have a chromosome like this? The only way that I can think of is if you're willing to say that the intelligent designer rigged chromosome number 2 to fool us into thinking that we had evolved. The closer we look at our own DNA, the more detailed a glimpse we get of our own genome, the more powerful the evidence becomes for our common ancestry with other species.

Note what Miller is really saying here: we have lots of evidence that we share common ancestry with the other great apes (heck, even Luskin has to admit that "humans and apes share a similar genetic structure") but, when we encounter something that raises a question how close that relationship is -- our different number of chromosomes -- and we go and look, we find convincing evidence that it is as close as we originally thought. If we hadn't found the fused chromosome, it would not have refuted evolution or common descent but it would have greatly changed our ideas about the relationship between gorillas, orangutans, chimps, bonobos and human beings. In short, it supports the other evidence that led us to think there was not just shared ancestry, but a close relationship.

What is Luskin's response to this evidence? Not wanting to go the "trickster Designer" route, he can only fall back on a presumption that there is a "Designer" and simply say that, if you look at the same evidence with their presumption, you can mangle it to fit their preconceived idea ... i.e. "the possibility that such biochemical similarities might result from common design upon a functional blueprint."

But why would a "Designer" abandon the "common design" of an already "functional blueprint" to fuse the human version of chromosomes 12 and 13, shared by all other primates? Now here is a research project that the Biologic Institute could take on: find the functional reason to fuse these two chromosomes. Otherwise, IDers are just offering a reason to ignore one piece of the massive total evidence, gathered across numerous lines of investigation in many different fields, that forms a consilience favoring common descent of all the great apes, including humans, and evolution in general.

Remember how Stephen Meyer crows about using "the same method of inferential reasoning that Darwin used," namely: "the inference to the best explanation"? When you take all the evidence, instead of selectively ignoring the evidence that your theory does not even attempt to explain, the best inference clearly favors common descent through processes that can be naturalistically explained.

And no amount of ankle biting can change that.

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Update: "NickM" asked in the comments if Luskin wasn't arguing that the originally created humans had 48 chromosomes which later fused; not that the creator fused them himself. If so, then the Biologic Institute wouldn't have to find the functional reason to fuse the two chromosomes (though there'd still be the question why the "Designer" didn't build in safeguards to prevent random fusing of chromosomes, which could be catastrophic).

But now we learn from Stephen Meyer (via Richard Hoppe at The Panda's Thumb) that:

If an intelligent (and benevolent) agent designed life, then studies of putatively bad designs in life–such as the vertebrate retina and virulent bacteria–should reveal either (a) reasons for the designs that show a hidden functional logic or (b) evidence of decay of originally good designs (Signature in the Cell, p. 497).

So, if the "Designer" didn't originally and intentionally fuse our chromosomes for some reason to improve his already "functional blueprint" for primates, there should be evidence that human chromosomes are inferior to the rest of the great apes. Still something the Biologic Institute could get its teeth into ... if it had any.
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