“Ontogeny Recapitulates Phylogeny”

Human embryo 4 weeks after fertalisation: about that tail...This must be something of a milestone: in Scientist Answers His Own Question Brian Thomas writes an entire post on evolutionary development without so much as mentioning Haeckel. Replacing mention of the supposedly fraudulent 19th century biologist we instead get an accusation of “begging the question.”

Usually as a last resort, Thomas does like claiming that the research he is commenting on is relying on this logical fallacy, or the related ‘circular reasoning.’ Because they reject evolution, creationists consider fair game any research that merely assumes that evolution occurs – which is everything, as devoting the introduction to your paper to proving that it occurred from, in effect, first principles would be a massive waste of everybody’s time.

Thomas opens:

Who wouldn’t be curious to learn why organisms “build tissues they seemingly never use,” as a Michigan State University News headline put it? If organisms originated from a string of trial-and-error natural “experiments” as evolutionary philosophy proposes, then they could be expected to grow useless leftover tissues—remnants of an inefficient evolutionary past—during embryonic development. While investigating this, one researcher answered his own question, showing how his research is “begging the question.”

What’s interesting here is that Thomas just assumes as self evident that, given evolution, the “leftover tissues” would appear. (It should not need explicitly stating that his explanation and terminology are as problematic as they are dismissive.) The researcher, on the other hand, actually set out to prove it.

The line “ontogeny recapitulates phylogeny” – a succinct way of stating the logic behind recapitulation theory – isn’t exactly dogma, and has indeed fallen out a favour. It is the idea that embryos should, as they develop, follow the stages of its descent from single-celled life forms to, say, a chicken. Of course, chicks do not look like (adult) dinosaurs at any point, so that’s a point against a simplistic understanding – instead, it’s the embryos of the ancestors that tend to be revisited. Ontogeny (developmental path) doesn’t always recapitulate phylogeny (evolutionary descent), perhaps not even very often, but it does it often enough to get the creationists worried. Why do we have tails in the womb? What’s with those other two sets of kidneys, which look suspiciously like the ones used by fish and amphibians? Gill slits in particular have come up recently.

This idea, at least when it comes to creationism, is rapped up in the true significance of vestigial organs. Creationists are often correct when they point to some function or another of the appendix and the like, but that’s not the issue here. Instead, it’s the fact that these new functions are obtained by re-purposing what’s already there, rather than starting from scratch as a design process would allow – and evolution is unable to do.

Out to demonstrate by simulation what would indeed seem to be a fairly self-evident conclusion was Jeff Clune: (paper, pdf, press release)

For a time, computer scientist Jeff Clune worked at Michigan State’s BEACON Center for the Study of Evolution in Action. He is the lead author of a study in the September issue of The American Naturalist that uses “digital organisms” to model how embryonic development, called ontogeny, supposedly rehearses an evolutionary past, called phylogeny.

What the Michigan part has to do with anything I couldn’t tell you.

Clune and his coauthors first “used a computational system that exhibits evolutionary dynamics.” They programmed simple digital organisms to “mutate, compete for resources and evolve.” Then, they “observed that ontogeny does indeed recapitulate phylogeny.” Well, wouldn’t it?

We can say that now, yes – but arguably, before this we didn’t know. I’d be interested to see this ‘system’ in action, actually – if it even has ontogeny it can’t be all that simple.

Programming imaginary creatures with “evolutionary dynamics” certainly helps to ensure that their resulting digital embryo facsimiles would reflect their imaginary evolution. This is begging the question, not practicing good science.

If using a model to show the consequences of a given assumption is indeed “begging the question, not practicing good science,” then we do have a problem – though not with the research.

Clune used an engineering metaphor to describe his team’s research. He told Michigan State News, “It’s comparable to building a roller coaster, razing it and building a skyscraper on the same ground. Why not just skip ahead to building the skyscraper?” But do embryos really build structures haphazardly, only to abandon them without reason?

Yes they do – see the examples given earlier. That’s a fairly good analogy, though for accuracy it might have been better to add that the skyscraper may use the foundations of the roller coaster. That would deal with the following:

Incredibly, Clune wrote, “Even if a structure is not actually used, it may set the stage for other functional tissues to grow properly.” If it is used to “set the stage,” then how can it be “not actually used?”

There’s really not that much to this article – Thomas is trying to deny everything and anything, weaving a confusing mess of accusations of various related fallacies. Ironically, he would have done better to have gone with something more akin to the Heackle argument. After all, if he could use this research to show that evolution predicts that ontology should recapitulate phylogeny, and then prove to us that this doesn’t happen, then he could have a proper case.

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