Invariant Cytochrome C Sequences Disprove Evolution?

The Creation Explanation is the web version of the book, of the same name, by Robert E. Kofahl and Kelly L. Segraves. In Part 7C they tell us about cytochrome c. Cytochrome c is an enzyme, a protein which helps an organism carry out chemical reactions. It like all proteins is a “string” of units called amino acids. There 20 different amino acids used in making proteins. (This is a bit simplified but it is good enough for our purposes here.)

Now the amino acid sequence of proteins vary somewhat from species to species. Scientists can used these variations to figure out evolutionary relationships. Now Kofahl and Segraves think they have a way to show that this is wrong. They give some cytochrome c data for 38 species. For each of these species they give the sequence from 62^nd to 84^th positions. Below I reproduce their data below. Each letter represents a specific amino acid. For a table for the abbreviations used please click here.

Now they tell us that

…there are regions in the protein amino acid chains in which the sequence of amino acids is identical in every cytochrome c. These are apparently parts of the molecule in which a very specific structure is essential for its enzyme activity.

In particular they point out positions 70 to 80 which I made green in the above:

The segment from positions 70 to 80 is invariant, for it is the heart of the active center of the enzyme molecule. In addition 24 other sites are also invariant. Another 23 sites are occupied by only one or the other of two very similar amino acids used in protein chains. There is no evidence for the evolutionary development of the overall structure of the enzyme nor of the active center and its function of catalyzing vital oxidation reactions in living cells. Thus the evidence supports the view that cytochrome c was designed, not evolved.

In short, they are claiming that the parts of cytochrome c which are most vital to its function do not change and thus show no evidence of evolution whatsoever. This claim has been in The Creation Explanation since its original 1975 edition which the acclaimed late biochemist Thomas S. Jukes responded to this in his “Molecular Evidence for Evolution”¹ published in 1983. He points out that if the invariance of parts of cytochrome c is supposed to be a sign of what Kofahl and Segraves called “intellegent purposeful design” than we can check this against additional data:

Why constancy of structure should be evidence of design rather than stability mediated by natural selection is not clear, but if Kofahl and Segraves mean to imply that variability of this segment [positions 70 to 80, in green above] would constitute falsification of their hypothesis of design, then their hypothesis must be taken as having been falsified.

Why? Because Dr. Jukes points out that the contrary to their claims, the segment in question is not invariant. All of the species which they gave data for are from the animal/fungi/plant clade which makes but a small part of life on Earth. Jukes compares the “invariant” segment from positions 70 to 80 with organisms more distantly related to us than what Kofahl and Segraves looked at. Lets look at two protozoans:

Now can almost hear some readers say that this is only two amino acids and now suggesting the same argument of Kofahl and Segraves for the remaining amino acids. This is a “moveable goalpost” argument. Every time a new residue is found to vary the argument would get changed to the remaining residues are invariant. This would not be a very useful hypothesis. After writing the above sentences I checked a list of cytochrome c sequences which I made to debunk another creationist cytochrome c claim. I notice that the carp’s “invariant” sequence differed in its first amino acid: NPKKYIPGTKM becomes BPKKYIPGTKM.

Now lets look at, as Jukes does, at something much farther away from us, a photosynthetic bacterium whose cytochrome c₂ has eight more amino acids in this segment than it than what any of the species we have looked at before:

Thus Jukes concludes:

Thus the conclusion by Kofahl and Segraves is based on an assertion of an invariance that does not exist. All that is evident is that evolution of this sequence takes place very slowly. Clearly, residues 70 to 80 do not change unless and until many other evolutionary changes have occurred.

Now as I pointed out above, the essay of Jukes was published in 1983. Kofahl and Segraves have continued to make revisions to The Creation Explanation including the section which we are discussing now. But this claim is still up nearly two decades after it has been indisputably shown to be in error. And even if they somehow missed the debunking, one would think that in the quarter century since 1975 they would occasionally check their claims against new data and would have discovered for themselves that cytochrome c was not invariant in the way they suggested. After they make this argument, they make use of Michael Denton’s data which involves comparing the very same Rhodospirillum rubrum cytochrome c₂ which we looked at above. Kofahl and Segraves might not have noticed that this disproves their ideas since one set of data was a direct sequence comparison and the other was a percentage comparison.

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