Information Increase in Evolution

I was looking up stuff on bacterial DNT degradation, and ran across a post by Joel Tay on antievolutionist criticisms based on “information”. It included an airy dismissal of an essay I had written back in 1999.

Wesley Elsberry writes in the second article:

When one takes the example of a tetraploid orchid and looks at a computable algorithmic information measure, the conclusion is that the tetraploid daughter species has more information in the genome than the diploid parent. This can be seen by simple experimentation with your compression algorithm of choice. Start with a base file. Compress and note the resulting size. Make a derived file that is composed of two copies of the original file. Run the compression algorithm again. Note that the resulting file size is strictly larger than that for the original file. Information content has increased by the computable algorithmic information measure.

This seems like an unhelpful analogy, because he’s talking about compression in a transmission sense (Shannon) rather than in a creating-new-proteins sense (Kolmogorov).

Uh, no, Joel. My little essay clearly approaches the information increase issue using two formal definitions of information (Shannon and Kolmogorov-Chaitin) plus an informal, “common-sense” version of “information”, and showed how a single biological example met the requirements for considering information to have increased by all three standards. How that example meets each standard is discussed separately. The compression discussed in the quote from my essay is exactly that considered by Kolmogorov-Chaitin algorithmic information theory, that of lossless compression of a string. It is not mistakable for “compression in a transmission sense”, at least, not if the reader is even partly paying attention. Also, the development of novel proteins is not necessary under any of those definitions to identify an increase in information.

Other than that, Tay has the usual sorts of antievolution bloviation about information. It all comes down to antievolutionist insistence that meaning and information should be conflated, plus a large dose of unreasonable doubt. An annoying feature of Tay’s post is the claim that Richard Dawkins never responded to a question about information increase by evolution posed by a antievolutionist videographer. The first comment in the thread posted the link to an essay-length response by Dawkins on that very topic. Tay’s response?

Regardless, the original question still remains unanswered, for nowhere does he give a sensible answer to the question, “Professor Dawkins, can you give an example of a genetic mutation or an evolutionary process which can be seen to increase the information in the genome?”

But Tay seems not to get the point that a response can exist even if he himself isn’t convinced of its veracity. In fact, Dawkins explored information increase in several different manners in his essay, which Tay (again) appears not to have read for comprehension. So since the question calls for an example, just one of those need be noted to demonstrate that Tay is in the wrong in his continued insistence that Dawkins never answered the original question. It is, indeed, eminently sensible, too. From Dawkins’ essay:

The dozen or so different globins inside you are descended from an ancient globin gene which, in a remote ancestor who lived about half a billion years ago, duplicated, after which both copies stayed in the genome. There were then two copies of it, in different parts of the genome of all descendant animals. One copy was destined to give rise to the alpha cluster (on what would eventually become Chromosome 11 in our genome), the other to the beta cluster (on Chromosome 16). As the aeons passed, there were further duplications (and doubtless some deletions as well). Around 400 million years ago the ancestral alpha gene duplicated again, but this time the two copies remained near neighbours of each other, in a cluster on the same chromosome. One of them was destined to become the zeta of our embryos, the other became the alpha globin genes of adult humans (other branches gave rise to the nonfunctional pseudogenes I mentioned). It was a similar story along the beta branch of the family, but with duplications at other moments in geological history.

Now here’s an equally fascinating point. Given that the split between the alpha cluster and the beta cluster took place 500 million years ago, it will of course not be just our human genomes that show the split – possess alpha genes in a different part of the genome from beta genes. We should see the same within-genome split if we look at any other mammals, at birds, reptiles, amphibians and bony fish, for our common ancestor with all of them lived less than 500 million years ago. Wherever it has been investigated, this expectation has proved correct. Our greatest hope of finding a vertebrate that does not share with us the ancient alpha/beta split would be a jawless fish like a lamprey, for they are our most remote cousins among surviving vertebrates; they are the only surviving vertebrates whose common ancestor with the rest of the vertebrates is sufficiently ancient that it could have predated the alpha/beta split. Sure enough, these jawless fishes are the only known vertebrates that lack the alpha/beta divide.

In other words, evolution produced the diversity of globin proteins, this diversity is in fact traceable in part via phylogenetic analysis, and the process that accounts for the diversity is gene duplication and subsequent divergence. What Dawkins gave an example of above is from the class of evolutionary change that results from such genetic duplication events with subsequent divergence. It is a sensible and understandable response to the original question posed to him, despite Tay’s predilection for airy dismissals. The capacity for antievolutionists to perseverate in error is well-illustrated by Tay.

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Wesley R. Elsberry

Falconer. Interdisciplinary researcher: biology and computer science. Photographer. Husband. Christian. Activist.