Luskin can’t see the reality of evolution for the trees (part 3)

Part 3 – Analysis and rebuttal (cont)

This post is the third part of a three-post series aimed at clearing up the misinformation written by the Discovery Institute’s Casey Luskin in regard to phylogenetic trees and  the idea of a complete tree of life (TOL).  In parts 3, 4, and 5 of Luskin’s series, he continues his bastardization of the evidence for evolution.

In part 3, Luskin discusses what he calls “extreme genetic convergence.”  The problem is that he confuses genetic convergence with heredity.

One data-point that might suggest common design rather than common descent is the gene “pax-6.” Pax-6 is one of those pesky instances where extreme genetic similarity popped up in a place totally unexpected and unpredicted by evolutionary biology. In short, scientists have discovered that organisms as diverse as jellyfish, arthropods, mollusks, and vertebrates all use pax-6 to control development of their very distinct types of eyes.

Having the same gene controlling eye development in different organisms is completely compatible with evolutionary theory.  This gene (pax-6) could have controlled the development of a very simple eye, perhaps a patch of photosensitive cells, in a common ancestor.  Subsequent organisms would use the foundation laid by pax-6 and add their own specific modifications to yield different eye types.  Luskin’s assertion here that pax-6 argues against evolution makes no sense, except for someone who is actively looking to twist data to their preconceived notion.

Luskin is also outright wrong when he says that pax-6 is used to “control development of their very distinct types of eyes.”  Pax-6 is necessary for eye development, but it does not influence the type of eye made.  For example, if you take the mouse pax-6 gene and put it into a fruit fly, the fruit fly makes fly eyes, not mouse eyes.  It is clear Luskin is either confused or is misrepresenting the facts.

Homology is evidence against evolution?

In part 4, he argues that homology between animals, both at the molecular level and at the physiological level, is a problem for evolution.  Luskin doesn’t really do any of his own work, but instead quotes from the Explore Evolution “textbook”:

To summarize, biologists have made two discoveries that challenge the argument from anatomical homology. The first is that the development of homologous structures can be governed by different genes and can follow different developmental pathways. The second discovery, conversely, is that sometimes the same gene plays a role in producing different adult structures. Both of these discoveries seem to contradict neo-Darwinian expectations

Neither discovery contradicts the theory of evolution.  It doesn’t matter the path that a gene or structure takes to be effective, it just matters that it is effective.  Explore Evolution is trying to take an interesting facet of biology and say it disproves evolution without really showing how common descent precludes these features.

Let’s turn the tables and ask what do these two discoveries mean for intelligent design? Well it means that here is another example of stupid design. I say stupid because what designer would use “different genes” and “different pathways” to come up with the same structure. That would be a monumental waste of time and effort for the designer. How about using the same gene for different functions? Well, that is better design, but it goes completely against the first point.

Morphological vs. phlyogenetic trees

In part 5 of Luskin’s series of posts, he claims that morphological data does not correlate with phylogenetic trees.   Maybe they don’t fit exactly, but the similarities are so common that it is ridiculous to think they are not due to common ancestry.  Like I mentioned in part 1, there is a lot of problems associated with the creation of mathematical models used to predict phylogenetic trees. Likewise, trees based on morphology are subject to their own problems.

To make his point, Luskin actually refers to the gene (cytochrome B) that I had picked in part 1 of my series of posts.  Using the sequence of this gene from different ape species,  I was able to produce the exact same phylogenetic tree as had been done using endogenous retroviruses.   What does Luskin say about cytochrome B?

pro-evolution textbooks often tout the Cytochrome C phylogenetic tree as allegedly matching and confirming the traditional phylogeny of many animal groups. This is said to bolster the case for common descent. However, evolutionists cherry pick this example and rarely talk about the Cytochrome B tree, which has striking differences from the classical animal phylogeny.

I didn’t look throughout all of “classical animal phylogeny,” but I was able to create evidence for common ancestry using cytochrome B that matched both morphological and molecular evidence.  Without common ancestry, this should not have been possible.

One final point. Whenever someone looks up scientific articles, it is best to look at the newest articles for obvious reasons. Yet Luskin did the exact opposite.  To help make his point here, Luskin quotes from several scientific papers that were published around the turn of the century.  One is even from 1993.  These papers came before the genomics era and before automated sequencing was common.  They do not really belong in this discussion.


Through his series of posts, Casey Luskin tries to portray the state of phylogenetic analysis as being counter to the theory of evolution.  I hope that I have showed that the opposite is true.  While we don’t have and may never have a complete tree of life, the data that we obtain creating trees or bushes is points squarely to common descent.


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