Pharyngula

Jonathan MacLatchie, the creationist who challenged me to answer his questions about development in Glasgow, has posted his account of our encounter and his problems with evolution. It is completely unsurprising — he still doesn’t understand any of the points.

Of his 10 questions, 7 were quickly dismissable and were more than thoroughly addressed in my talk. They rest on a deep misconception that is shared with Jonathan Wells and many other pseudoscholarly creationists; I can summarize it with one standard template: “Since Darwinian evolution predicts that development will conserve the evolutionary history of an organism, how do you account for feature X which doesn’t fit that model?” To which I can simply reply, “Evolution does not predict that development will conserve the evolutionary history of an organism, therefore your question is stupid.” It doesn’t matter how many X’s he drags out, given that the premise is false, the whole question is invalid. But they can play that rhetorical game endlessly, citing feature after feature that doesn’t fit their misunderstanding of the science, making it sound to the clueless like they’ve got a legion of contradictions with evolution. Unfortunately for them, their objections are to creationist evolution, which has very little relationship to real evolution.

The gist of my talk was that Haeckel was wrong, that there was no recapitulation of developmental stages. Variation can and does occur at every stage of development; early and late stages vary greatly; evolution does not proceed primarily by terminal addition of new stages, as Haeckel postulated; but there is an interesting and real convergence on the broad, general outlines of the body plan at one point in development that needs to be explained.

MacLatchie’s response, greatly abbreviated, is to say that recapitulation doesn’t occur; variation occurs at every stage of development; early and late stages vary greatly; and look! I have papers from the peer-reviewed scientific literature that agree with me! Well, yes. That’s what I said. That is the conventional, ordinary, normal, well-understood, evolution-compatible side of the story from the scientists, like I’d been saying. Is there an echo in here, or do you just not understand what you heard or what you read, that you think the facts are evidence against evolution?

Apparently, in the Q&A for my talk (which you can now listen to; MacLatchie is first up), he asked me, I think, question #3 from his list, but I couldn’t really tell. As is typical, he turned it into a long-winded turgid mess, and I’ll be honest, I really couldn’t grasp what he was trying to ask, and I think he was actually getting at two different things. One is that there are differences in the embryological origins of some organs; this bothers him, apparently, because he’s sitting there expecting that there shouldn’t be any differences in how, for instance, the neural tube forms, because it’s a primitive structure, and therefore, because development is supposed to recapitulate evolution, they should be identical. I missed that; I was trying to see a more intelligent question in his verbiage. Now that I’ve read the papers he was waving around, I can answer a little differently: yes. There are differences in how different organs form in different species.

So?

It is not a tenet of evo-devo that primitive structures must follow identical ontogenetic pathways. We actually understand that divergence can occur at all stages of development.

The other thing he was getting at was something I thought I understood when I tried to get him to focus on one example, and suggested neural tube formation. There what we see despite differences between species is a widely conserved molecular homology — that there is an interplay between BMP and Dpp in defining the prospective nervous system in flies and vertebrates. These deep homologies in organization were not expected and not predicted by evolutionary biology, but their presence does imply evolutionary affinities. That there are differences — for instance, a frog will form a hollow tube by folding the sheet of the neural plate, while a fish seems to submerge the sheet into the body and then secondarily cavitate* — are real, but relatively superficial. And differences are not precluded by evolutionary theory!

I wish I could get that one thought into these guys heads: evolutionary theory predicts differences as well as similarities. Finding a difference between two species does not send us rocking back on our heels, shocked that such a thing could be.

There’s another weird thing in that clip that is so typical of creationists. He pointed at those papers of his, dropped a few scientists’ names, and claimed they all supported his position. They do not. He gave me copies of three of them afterwards; two I’d already read and was fairly familiar with. Come on, he was citing Pere Alberch, the great synthesizer of development and evolution, in support of intelligent design creationism?

MacLatchie doesn’t even understand the paper. What Alberch is doing in it is arguing that many efforts to use developmental information in systematics go wrong because they have a creeping Haeckelian interpretation, that the sequences of events in development should preserve the evolutionary sequence. They don’t, he said, and as I also said, Haeckelian recapitulation is false. So, once again, MacLatchie was confronting me with a paper that confirmed what I had said as if it somehow showed I was wrong. I really don’t get it.

It’s also a subtle example of quote-mining. In the paper, Alberch gives two examples of developmental variation in vertebrates, describing differences in toe number and in the mode of neural tube formation. MacLatchie quotes him this way:

According to the Alberch paper (the claims of which remain true to this day), it is noted that it is “the rule rather than the exception” that “homologous structures form from distinctly dissimilar initial states.”

First, it’s a slightly odd quote: the two phrases are from two different paragraphs, and are in the reverse order from how they’re written here. He doesn’t substantially change the meaning, though, so it’s not quite as nasty as the usual scrambling. (However, it is peculiar that this same exact cut & flip quote can also be found in the works of Harun Yahya, and who knows where he got it; it’s just another example of creationists copying each other.)

However, this is where it gets devious. MacLatchie omits to mention the very next sentence after part of that quote:

The diversity of tarsal morphology, as well as the variation in ontogenetic pathways leading to the formation of the neural tube, reflect variations in developmental parameters or initial conditions within conserved developmental programs. [emphasis mine] There is structural organization in this scheme that should be amenable to systematic analysis but the information in not in the ontogenetic sequence.

You see, that’s the point of his paper: it’s a criticism of naive interpretations of developmental processes that are built on Haeckelian assumptions that the sequence of stages will be evolutionarily conserved. They aren’t. This does not represent a denial of evolutionary relevance; quite the contrary, he goes on to propose better ways of examining the role of development. After giving some examples, he explains that better methods “share the common emphasis on regulation within a resilient developmental program, and they emphasize the need to go beyond the perception of ontogeny as a sequence of discrete developmental stages.”

It’s actually surprisingly offensive to see creationist citing the late Alberch as somehow supporting their lunatic views. I suddenly feel like I was not rude enough to MacLatchie at that talk.

It’s a superficial ploy creationists play. They don’t have any scientific literature of their own, so they go rummaging about in the genuine scientific literature and start pulling out fragments that show disagreement and questions in the evolutionary community. And that is so trivial to do, because they don’t grasp something obvious and fundamental: every science paper has as its throbbing heart a question and an argument. Seriously. Every single paper on evolution is arguing with evolution, probing and pushing and testing. I am not at all impressed when some clueless dingbat pulls up Alberch’s paper titled “Problems with the interpretation of developmental sequences” and crows about finding a paper that talks about “problems”. Problems are what we’re interested in.

In an attempt at turnabout, MacLatchie also tries to claim that I distorted Jonathan Wells’ position by implying that Wells does not try to use Haeckel’s errors to undermine the foundations of evolution, because Wells openly explains that Haeckel was discredited by his peers.

A casual reading of chapter 3 of Wells’ The Politically Incorrect Guide to Darwinism and Intelligent Design (which was cited by Myers) reveals that Wells, in fact, tells us that “Haekel’s fakery was exposed by his own contemporaries, who accused him of fraud, and it has been periodically re-exposed ever since.”

Why, yes, it’s part of Wells’ game. He declares that Haeckel’s theory has been thoroughly rubbished, and therefore the foundations of ‘Darwinism’ have been destroyed. Note the sneaky substitution: Haeckel’s theory is not the foundation of evolution. We can kill it, kick it when it’s down, run it through a woodchipper, and it just doesn’t matter — it’s not part of evolutionary theory. I’ve dealt with this subterfuge at length, so I don’t really need to go into it again, do I?

*Which has since been found to be less of a difference than thought before. The fish neural tube does fold, but the cells are more tightly adherent to one another so you don’t see the central ventricle forming as obviously.


I said 7 of the 10 questions are blown to smithereens by the simple fact that they are built on false premises — MacLatchie doesn’t really understand that Haeckelian recapitulation is not part of evolutionary theory. I’ll quickly answer the remaining three right here.

4) Could you please explain the near-total absence of evidence for evolutionarily relevant (i.e. stably heritable) large-scale variations in animal form, as required by common descent? “Near-total”, that is, because losses of structure are often possible. But common descent requires the generation of anatomical novelty. Why is it the case that all observed developmental mutations that might lead to macroevolution (besides the loss of an unused structure) are harmful or fatal?

This is just like the standard creationist claim that there are no transitional fossils: there are no transitional mutations, either! When we see variations in morphology between populations of organisms, how did those changes get there, were they implanted by angels? As clear examples of “transitional mutations”, I’d point to polyphenisms, cases where there are discrete differences between genetically identical individuals based entirely on their environment.

I also suspect that the poorly explained basis of his question is that lab-generated mutations tend to be changes of very large effect on single genes. Polygenic phenomena are much harder to pick up and harder to analyze, and subtle variations in a fly or a worm are hard for us humans to detect, so the reason we see big, harmful mutations in the lab is because we’re looking for big, harmful mutations.

One more thing: look at sticklebacks. We find gross variations in form, armor, and spines that are caused by tiny changes in gene regulation.

8 ) On your blog, you have defended the central dogmatist (gene-centric) view that an organism’s DNA sequence contains both the necessary and sufficient information needed to actualise an embryo’s final morphology. If your position is so well supported and the position espoused by Jonathan Wells (and others) is so easily refuted, then why do you perpetually misrepresent his views? For example, you state “These experiments emphatically do not demonstrate that DNA does not matter … [Wells’] claim is complete bunk.” Where has Jonathan Wells stated that DNA “does not matter”? Moreover, contrary to your assertions, the phenomenon of genomic equivalence is a substantial challenge to the simplistic “DNA-is-the-whole-show” view espoused by the majority of neo-Darwinists. Cells in the prospective head region of an organism contain the same DNA as cells in the prospective tail region. Yet head cells must turn on different genes from tail cells, and they “know” which genes to turn on because they receive information about their spatial location from outside themselves — and thus, obviously, from outside their DNA. So an essential part of the ontogenetic program cannot be in the organism’s DNA, a fact that conflicts with the DNA-centrism of neo-Darwinism. Some attempts to salvage DNA programs (e.g. Rinn et al.) rely on “target sequences” — molecular zipcodes, if you will — of amino acids that direct proteins to particular locations in the cell. But such “molecular zipcodes” do not create a spatial co-ordinate system, they presuppose it.

This one is totally hilarious. First sentence: he claims I advocate a central dogmatist (gene-centric) view that an organism’s DNA sequence contains both the necessary and sufficient information needed to actualise an embryo’s final morphology, and to support that, links to one of my articles where I supposedly get all totalitarian for dogmatic genecentrism. Go ahead, follow the link. I say exactly the opposite.

10) Why do Darwinists continue to use the supposed circuitous route taken by the vas deferens from the testes as an argument for common descent when, in fact, the route is not circuitous at all? The testes develop from a structure called the genital ridge (the same structure from which the ovaries develop in females, which is in close proximity to where the kidneys develop). The gubernaculum testis serves as a cord which connects the testes to the scrotum. As the fetus grows, the gubernaculum testis does not, and so the testis is pulled downward, eventually through the body wall and into the scrotum. The lengthening vas deferens simply follows. And, moreover, before the vas deferens joins the urethra, there needs to be a place where the seminal vesicle can add its contents.

Wait, what? The route isn’t circuitous? I don’t know about you, but my testicles dangle down right next to my penis, yet the plumbing connecting them has to go back up into my torso, then down and around to exit in just the right place, a few inches away. And yes, there has to be a fluid contribution from the prostate, but again, that organ is tucked away inside, away from the action. And why do the testes have to be dangling anyway? Put ‘em up next to the prostate. It would make far more sense.

Sure, you can put together physiological explanations for why each of those organs is in its particular place, but it doesn’t change the fact that the whole assemblage is a contingent kluge stuck together opportunistically.