Thursday, February 24, 2011

A False Echo of Discontinuity

Much to my dismay, my sister gets a monthly magazine (at the request of her Bible teacher) from the Institute for Creation Research called Acts & Facts. I've peeked into it a few times, and it seems pretty shallow in general, but there are articles here and there that actually make tangible claims about evolution. Last month's issue included a short article called "Molecular Equidistance: The Echo of Discontinuity?", written by Nathaniel T. Jeanson.

Jeanson examined cytochrome b, a gene found in almost all organisms. Here's the data that the article focuses on.

The more closely related two species are, the more similar their genes are, which constitutes powerful molecular evidence for evolution. A human's cytochrome b gene is 79% similar to a panda's, 75% similar to a tortoise's, and so on. However, as Jeanson points out, yeast's cytochrome b is equally similar (50%) to all the other animals on the list. He claims:
"Evolutionists hail the ordered, hierarchical pattern of human-to-other-species comparisons (depicted in the leftmost column of the table) as a fulfillment of the predictions of [evolution]. However, as Michael Denton observed ... the rows of data depict something entirely different. As demonstrated by the comparisons of yeast to every other creature in the table (depicted in the bottommost row), the yeast cytochrome b cannot be arranged in any sort of hierarchy with the other creatures; yeast is equidistant from all other creatures. Hence, it appears that yeast cytochrome b is isolated, separate, and completely distinct from all other species in the table—it is as close to beetles as it is to humans! In a sense, yeast appears discontinuous from the other creatures in the table. This is consistent with the predictions of Genesis 1."
Initially I was surprised by this assertion, and it seemed reasonable on the surface (although how exactly this was "predicted" by Genesis is unclear). But then I noticed Jeanson's reference to Michael Denton's book Evolution: A Theory in Crisis, which had apparently done the same thing with cytochrome c, and it occurred to me that this claim may have been dealt with before. I was right, and as soon as I saw the criticism of Denton's work, everything clicked.

I'll try to explain with an illustration. Below is a hugely simplified graph I created to show genetic divergence. The numbers in blue represent pieces of genetic information that are modified by mutations over time.

This might be a bit confusing, but stare at the numbers for a while and the pattern should become clear. The four different digit positions are there only to distinguish between mutations before and after each speciation event. In this simplified model, each type of animal undergoes one mutation at each time point, represented by the number at one of the positions increasing by one; higher numbers mean greater divergence. We'll call the leftmost digit position "first position," followed by second, third and fourth.

Now let's do a bit of arithmetic. How many "genetic divergence units" away are reptiles from mammals at Point #5? They differ by 2 in the third position and 2 in the fourth position, which makes 4 units altogether. Amphibians differ from mammals by 3 in the second position, 1 in the third position, and 2 in the fourth position, for a total of 6 units. Finally, fish differ from mammals by 4, 1, 1 and 2, for a total of 8 units. These relationships mirror the columns in Jeanson's table.

Now, how many units away are fish from amphibians at Point #5? They differ by 4 in the first position and 4 in the second position, or 8 units total. If we do the same with fish/reptiles and (again) fish/mammals, we find that these pairs are also 8 digits apart. This mirrors the rows of Jeanson's table.

So why do we get these results? The most important thing to recognize is that amphibians have spent just as much time undergoing mutations and diverging from fish as reptiles and mammals have. However, the same is not true if we look at it in terms of mammals: in this graph, reptiles and mammals have the same evolutionary trajectory for a long time (until after Point #3), amphibians and mammals for a medium amount of time, and fish and mammals for short time. Naturally, the longer two animals share an evolutionary history, the more similar their genetic information will be. The results we get here and the results in Jeanson's article are exactly what evolution predicts. (If this explanation was unclear, the one in the second half of this review may be helpful.)

Here's the bottom line: Jeanson is utterly and undeniably wrong. And he's not just wrong: he borrowed a faulty argument from a 25-year-old book to use as the central thesis of his article. Then the fine folks at Acts & Facts took that article and published it. Apparently neither party thought it might be a good idea to see if there had been any criticism of that work over a period of two and a half decades.

Jeanson and Acts & Facts are either totally ignorant of the fact that Denton's argument has been refuted, not smart enough to understand that refutation, or too dishonest to care about it. And now thousands of creationist readers will add another piece of illusory evidence to their arsenal of falsehoods. Whenever I dig deeper into a creationist claim, this is what I get. It's enough to make me wonder whether I should even bother.

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