Evolution in the News - November 2003
by Do-While Jones

Incongruence

Have evolutionists finally solved the DNA dilemma?

Evolution depends upon determining the supposed phylogeny (ancestral relationships) between various species. “Cladistics” is one method that has been used to do this, generally without success.

[There] was endless argument, because a phylogeny supported by analysis of one gene would often be very different from that created using data from another. Retreating into statistical thickets, researchers had to employ more or less sophisticated criteria to decide which of many millions of possible trees was most likely to represent the true history of the group in which they were interested. 1

Last month, Nature published an article 2 in which the authors claimed to have determined the “true” evolutionary relationship between eight different kinds of yeast by analyzing 106 different genes.

Rokas et al. started with 106 genes represented by orthologues in all their candidate species, and then computed phylogenies using each gene in turn. As had been expected, each gene supported its own particular branching order. In other words, the trees were 'incongruent'. 3

In plain English, depending upon which of the 106 genes they chose to analyze, they got one of many different relationships. That is, if they looked at one gene, it would show that yeast A was more closely related to yeast B than yeast C; but if they chose a different gene to analyze, it said that yeast A was more closely related to yeast C than yeast B.

Notice, it “had been expected” that one would get different results depending upon which gene was selected. The editor of Nature didn’t say, “We were shocked that different genes suggested different family trees.” No, they expected the results to be “incongruent” because that’s what normally happens. Unfortunately, this information has been kept secret from the people who responded to Roberto’s question. They think that DNA analysis is always consistent, and always agrees with the family relationships paleontologists propose based on the fossil record. It is too bad those people don’t read Nature or Science.

The authors of this study came up with a way to use all 106 genes and came up with the “true” evolutionary tree. (Well, actually, it is more like an evolutionary twig because they are just dealing with eight kinds of yeast, not eight diverse species.)

… the authors are making an unprecedented claim: that this is a fully resolved phylogeny with five internal branches in the tree, each of which has unequivocal support from all the data. For years biologists have tried to find methods to tease evolutionary history from obtuse data. This looks like the best attempt yet. 4

That summary was written by a senior editor at Nature, the journal that published the article. Naturally, Nature would not have published the article if the editorial staff thought it was without merit. But they aren’t willing to go too far out on a limb of that evolutionary tree. This is merely the "best attempt yet" to "tease evolutionary history" from DNA. The editor ends his review by saying,

There may be no way to know, without question, how many data are necessary to create a perfectly resolved tree, or indeed if this tree is necessarily the 'true' tree. But evolutionary biologists, like scientists generally, can only ever deal in provisional solutions. 5

So, this is “true” today, but it might not be true next month. Since truth is so provisional, why are evolutionists so dogmatic about it?

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Footnotes:

1 Gee, Nature Vol. 425, 23 October 2003, “Ending incongruence”, page 782 (Ev)
2 Rokas, et al., Nature, Vol. 425, 23 October 2003, “Genome-scale approaches to resolving incongruence in molecular phylogenies”, 798 - 804 (Ev)
3 Gee, Nature Vol. 425, 23 October 2003, “Ending incongruence”, page 782
4 ibid.
5 ibid.