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Creationism: Wasting My Time on Lysozyme
I've mentioned before that I get daily articles put out by Answers in Genesis. They've been serializing some books, and the latest is Creation: Facts of Life by Gary Parker. It has been around since at least 1980, but the most recent version is from 1994.
As I read the first chapter my baloney meter was going off. The chapter attacks the whole concept of homology with the old argument of: 'features are similar because of common design, not common descent.' As I read some of the specific examples I began to be very suspicious. First of all, I'm always suspicious when a creationist quotes mainstream scientists in support of a creationist argument. I'm even more suspicious when a creationist asserts a fact that is so obviously counter to evolution that it would seem that scientists must be either fools or agents of evil to go on in the face of it.
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I won't get into all of the chapter--I've wasted enough time on it already. I will limit my discussion to this claim:Lysozyme is the enzyme in tears that “bites holes” in the cell walls of bacteria so that they explode. (Listen for the “pop” on a quiet evening!) Egg whites are rich in the same enzyme, and that’s what keeps eyes and egg whites from getting easily infected.
Objective evidence shows that human lysozyme is more closely related to that of chicken than any other mammal? Well, let's look into that one.
By comparing lysozyme and lactalbumin, Dickerson was hoping to “pin down with great precision” where human beings branched off the mammal line. The results are surprising. In this test, it turned out that humans are more closely related to the chicken than to any living mammal tested! Every evolutionist knows that can’t be true, but how can he get around the objective evidence? In his concluding diagram, Dickerson slips in a wiggly line for rapid evolution, and that brings the whole thing back in accord with his evolutionary assumptions. But notice that his protein data, the facts that he observed, did not help him at all with his evolutionary idea.
First of all, the quote from Dickerson comes from a 1969 book--not really accessible. But from what I can find, Parker is apparently mangling a discussion about rates of evolution. (I'll explain in the comments if anybody really wants me to.)
The lysozyme claim has been around since at least 1980, and keeps popping up even though it has been repeatedly refuted. (See here, here, and here for background.)
A more recent book by a different author (2000) that claims to have up-to-date information apparently also repeats the claim, since it is contained in the free accompanying study guide (pdf).
So for fun, I poked around on a publicly accessible database to see what I could find. Below, I show the first third (approximately) of the amino acid sequence of lysozyme from human, chimpanzee, mouse, and chicken. I don't have software at home to do it for me, so I went through the sequences and highlighted any differences from the human sequence by hand. 
Lo and behold, human and chimpanzee are the same, mouse is somewhat different, and chicken is the most different. Now this is only a portion of the sequence, but it is pretty obvious that the claim that chicken is closer to human than any mammal is false.
So there you have it. I've spent more time than I should have on this claim. I hope you've enjoyed it.
2 comments:
What I understood him to be claiming was not that the chicken is closer to humans than any other mammal, but rather that the human is closer to the chicken than any other mammal. While I still think that it's a crock, I wonder if you made a chart (which wouldn't have much of a pattern to it at all) which showed the difference not from a human, but from a chicken how it would turn out.
Let's step back and re-phrase. I understand him to be saying the following: that the human gene (lysozyme) is more like the chicken gene than it (the human gene) is like the gene of other mammals. In other words, the human gene clusters with the chicken gene to the exclusion of other mammals. This is false, as I've shown above.
Another intepretation is this: the human gene clusters with other mammalian genes, but of all mammalian genes, the human gene is most similar to chicken. In other words, human clusters with mammals, but human is more similar to chicken than any of the other mammals are. Stated this way it is also false because human and chimpanzee are the same--and maybe gorilla too. But if we look past that and assume that the basic assertion is true, this argument seems to get at why chicken lysozyme is more similar to a derived mammal rather than a more primitive one. That would be an interesting question that I don't think would be too hard to answer (again, assuming it were true), but that is a substantially weaker argument than the first interpretation above. It's like saying that since a Japaneese gene is more like a Navajo gene than any of the other Native American tribes (implicitly acknowledging that the Native American tribes cluster together) then common descent from ancient Asians is false and therefore God created each tribe separately.
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