Sunday, April 02, 2006

Junk science

Last week PZ Myers brought the excellent post he wrote about my paper on the evolution of cell lineage complexity back from the archives. In a related post, PZ took the opportunity to remind us of how Paul Nelson, a fellow of the Discovery Institute, claimed our paper offered "a workable (i.e., usable) measure of ontogenetic depth, maybe". Ontogenetic depth was a concept proposed by Nelson in an unpublished discussion paper in early 2003. I first heard of Paul Nelson and ontogenetic depth in Pharyngula. The ignorance, apparently, was mutual, even though our measure had been originally published in 2003. Despite insistent requests for clarification, and repeated assurances that "an omnibus reply" was in the making, Paul Nelson hasn't said anything substantive about ontogenetic depth for two years. PZ concludes:
"Nelson promised us an explanation of his method; months later, after giving us nothing, he showed up to point to a legitimate and interesting science paper that used an interesting technique, apparently nothing like what he was doing, and thinks that's a fair substitution? What a wonderful example of the purely parasitic nature of the Discovery Institute! No work, only promises, and the best they can do is point to the efforts of real scientists!

We're still waiting for Paul Nelson to explain the procedure and utility of "ontogenetic depth". A day wasn't enough, and I can't complain about that. A month was pushing it. A year? That's not looking so good. At two years, we ought to just give up. I'll be patient, though, and give the poor fellow a decade [...]"
Last week I encountered another example of this kind of scientific parasitism by another intelligent design creationist: Salvador Cordova. Cordova, like Nelson, regularly engages in polite discussions with evolutionary biologists. This time, the topic was "junk" DNA. Cordova joined the discussion and steered it towards the topic of robustness. Over a two comments, he wrote:
"One can do a knockout experiment on one of the develomental pathways of a nematode vulva and then an alternative develomental pathway kicks in to create the vulva. There are two independently successful redundant developmental pathways in the vulva. [...]

In the case of the nematode vulva, without some co-option, the independent path way can not be selectively advantaged unless the other develpmental pathway is knocked out. The independent pathway, would have to be pretty much functional when it appears as it is critical to perpetuation."
He then used this example to suggest that robustness cannot evolve. The problem is that his discussion of vulval development in Caenorhabditis elegans is rubbish. The fates of the six vulval precursor cells are determined by the action of two signaling pathways: the EGF receptor/RAS/RAF/MAPK inductive signaling pathway specifies the primary vulval fate, and the LIN-12/Notch lateral signaling pathway specifies the secondary fate. However, these pathways are certainly not redundant.

The redundancy he's thinking about is in the synMuv (synthetic multivulva) genes. These form two functionally redundant classes, A and B (to which a third, C, has recently been added), of regulators of RAS signalling. This class of genes gets its name from the observation that mutants from within a single class show normal vulval development, but double mutants affecting loci in different classes, known as "synthetic", show several ectopic vulvae, a phenotype known as "multivulva". However, the synMuv genes do not constitute "independently successful redundant developmental pathways". This is parasitism of the highest order: the synMuv genes were originally characterized in the lab of the Nobel Prize winner Robert Horvitz. Let's just say that he's no intelligent design creationist. When are you guys going to start doing some actual research, instead of misinterpreting the work of real scientists?

Cordova's other arguments on how robustness evolves (or rather fails to do so) bear no relationship to any real research into this problem -- for a proper review of the subject see, for example, Andreas Wagner (2005), de Visser et al. (2003) or Flatt (2006). For example, commenting on A. Wagner's paper (reviewed here and here) Cordova descended further into his strange world of make-believe:
"Regarding the paper pertaining to circadian oscillators, 'Can these results be generalized to other systems? It's impossible to tell at this stage.' The answer is likely no.

We know from mathematics that evolutionary algorithms can only solve a small fraction of design architectures. That is a given fact in engineering. Some of those architectures which evolutionary algorithms can not solve are already in evidence in biology, such as the turing machine or anything dealing with large scale software such as seen in the cell."

Notice how Cordova skiped over the entire argument from the paper without actually addressing what Wagner set out to test, and then made up some "given facts" about evolutionary biology.

Remember Cordova's prediction that Wagner's result cannot be generalized to other systems. For the record, I'll bet on the opposite outcome. I'll return to this as more evidence comes out. (Something tells me that you won't have to wait for too long.)