Some evolutionists are thoughtful and measured, willing to admit the anomalies that evolutionary theory must still explain. Richard Dawkins is not one of them. Instead, he seems to inhabit a la-la land where all the conceptual difficulties connected with the evolutionary theory are resolved or swept under the rug. As one colleague who wishes to remain out of the limelight wrote to a list I moderate:
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In the MSNBC interview with Richard Dawkins, titled “The Not-So-Angry Evolutionist,” Dawkins says the following:
“You can actually plot a picture of the pattern of resemblances and differences between every animal and plant and every other animal and plant, and you find out that it fits on a beautiful, hierarchical, branching tree, which can only sensibly be interpreted as a family tree. When you do the same thing with a different gene, you get the same tree. Do the same thing with a third gene, and you get the same tree. It’s overwhelmingly powerful evidence.”
It’s also overwhelmingly false. No molecular systematist would make this claim.
Now, either Dawkins knows this, and therefore is lying to his audience, or he doesn’t know, and has been cribbing from erroneous Talk.origins FAQs. Either option is bad news. One should not accuse someone of lying without solid evidence, so let’s just say that Dawkins is wildly irresponsible.
The incongruence of gene and species trees is a standing obstacle, or research problem, in molecular phylogenetics. Look at figure 2, for instance, from this paper (open access — you’ll need to click on the figure to enlarge it):
http://genomebiology.com/2007/8/6/R109
Note that all possible topologies, among the groups considered, are supported by significant numbers of genes.
In the context of Dawkins’s claim, this means that gene A supports grouping X, but gene B supports grouping Y, whereas gene C supports grouping Z, and so on. In short, one doesn’t get the same species tree from any given gene. This problem of gene and species tree incongruence is so widely known in molecular systematics that it now arguably represents an entire field of study.
Huertas-Cepas et al., the authors of this paper, note:
“The finding that all three possible topologies, including the one widely considered as wrong in the literature, are supported by a significant number of trees illustrates the inherent difficulty of resolving the species phylogeny from gene phylogenies. We have found similar topological diversity in the three scenarios considered (see below) and also, to smaller degrees, in apparently undisputed evolutionary relationships (results not shown). Similar results showing variability in the relative positions of arthropods, nematodes and chordates have also been found in topological analyses of the phylogenies of 507 eukaryotic orthologous groups and of 100 protein families. These deviances from the species phylogeny might be the result of different processes, including convergent evolution or varying evolutionary rates.” (2007, 8R:109; emphasis added, endnote numbers omitted)
In a commentary on Huerta-Cepas et al. 2007, Castresana observes:
“Just getting the best-supported topology is not enough, and even using all genes in a genome may not help you come to an unambiguous solution. This is because different genes produce different biases, and rigorous criteria for selecting the genes to be used to build a species tree are necessary to get less ambiguous results, as has been done in other work… The important message from this part of the study is that, whatever the true tree may be, trees derived from single genes are more likely than not to point to a wrong topology.” (2007, 8:216; emphasis added)
Caveat lector for Dawkins’s new book.