Cytachrome C and neutral drift

Yes, Cytochrome C is part of the evidence for common descent. It is a highly conserved protein, so it only picks up very few changes. The patterns of difference fit the nested pattern of differences inferred by other means, which is a reflection of diverging lineages from common ancestors.The full strength of the evidence is not from a single protein, but the mutually confirming evidence of many genes and proteins. I have not read the paper you cite in detail yet; but it looks interesting. It considers not only the gene coding for this protein, but a closely related pseudogene.The Cytochome C protein is of special interest in the evolution/creationism debate, because of a creationist argument that used to be raised. It turns out that snakes have a sequence which is unusually close to the primate sequence, which means that snakes may place incorrectly in a phylogeny, especially if there are not a lot of close relatives for snakes included in the analysis, and if raw distances are used rather than a proper cladistic analysis. This is sometimes taken by creationists as undermining the case for common descent.Cheers -- Sylas

I don't get your point. You do know that "sharks" is not a species, I presume. I would expect certain amount of diversity in Cytochrome C within sharks. The amount of variation depends, amongst other things, on the time back to their most recent common ancestor. We should expect patterns of diversity that tend to line up well with phylogeny obtained by other independent means. Comparison with rays would be good also (I think they are close relatives).Do you have any information available on how much diversity in Cytochrome C there is between different species of shark?Cheers -- Sylas

No, the writer is not correct.First, sharks are not a species; they are many species.Second, sharks most certainly have changed over millions of years. They are very successful in their niche, and so ancient sharks are still very clearly sharks, so the basic body form we recognize as "shark" has been around for a long time; but it is not unchanging.Third, I would expect there will be some minor differences in cytochrome C sequences within some species; but that this will be unusual. This is because the sequence is so highly conserved. To test this would require many sequences from a single species. I do not believe the writer has such data. Most species, however, will tend to have a single uniform cytochrome C sequence, because of the strong conservation.Fourth, actually, I think there is cytochrome C variation within sharks. As has been pointed out, your other reference was actually for COX (I missed that, oops!). I can't find a reference for several shark species and cytochrome C; but someone with a bit of time might like to trawl the databases and find out directly. There is certainly variation in cytochrome B; reported in Protein evolution in different cellular environments: cytochrome b in sharks and mammals, by AP Martin and SR Palumbi, in Molecular Biology and Evolution, Vol 10, 873-891. (July 1993).Cheers -- Sylas