Ontogenetic Depth

Great. What did you get out of it?

In the first instance, the answers to pretty well all the objections raised in the thread.

Secondly, the realisation that none of the posts offered any explanation for the conundrum Paul raised.

Great. You should consider providing those answers, since Paul apparently won’t do that here.

So far, I don’t even know what the conundrum means. His three numbered claims don’t seem to add up to any sort of problem. Again, perhaps you can explain where he won’t.


Where I come from, everyone studies the presentation first, and then discusses it.

My brother is a non-scientist, and when I sent him a paper he said, “Of course, I jumped to the conclusion first, and it was rubbish.” I expect more from academics, or else I will give same engagement I gave my brother, ie none.

If an argument can be made in a blog comment, you don’t need a video presentation in the first place.

Where I come from, people present ideas in a more concise form than a 1-hour video. I did study the written presentation before discussing it.

In what way does the existence of Dictyostelium not falsify each of the premises?

Where I come from, science is not communicated by video. Are you incapable of putting his arguments into words on the page? What problem does ontogenetic depth pose for evolution?


Citations aren’t necessary; this is high-school level biology.

  1. The Metazoa (the animals) are eukaryotes; the last universal common ancestor of Eukarya (LECA) was a single-celled organism. Therefore the Metazoa evolved from a single-celled eukaryote. Whether, along that lineage, something existed akin to Dicty (which is not a metazoan and branches off in eukaryotic phylogeny much earlier than the evolutionary events in question here) may or may not be the case, but Dicty itself is irrelevant to the puzzle of OD, as it pertains to the origin of animal cell differentiation. If you claim relevance, you should show how a Dicty-type alternation of generations explains the origin of the early cleavage stages of any animal. C. elegans is the example in the video, which I chose because the model system is so well-understood.

  2. Any sound definition of natural selection includes reproductive capability as a necessary condition.

  3. As Roy noted above, the exact timing of the onset of reproductive capability may vary in certain groups (neoteny), so I need to qualify my remark about reproductive capability arising at the end of development. But, with that caveat, development must proceed well downstream before an animal can produce gametes – far enough downstream, that is, for the cell type “gamete” to be fully differentiated and capable of release, fertilization, cell division, etc.

Did you watch the video?

OK, I’m guessing that you propose an extreme version of Haeckel’s law. Since reproduction happens at the end of ontogeny, it must also happen only at the end of phylogeny. But since phylogeny requires reproduction at the start, evolution is impossible. Is that it? If your claim is something less ridiculous, please, I beg of you, make your claim explicitly rather than assuming we all see the problem. I for one do not. And Dictystelium doesn’t have to be in the metazoan lineage to offer an example of an intermediate form. Ancestry is not a requirement. That’s why Darwin was able to use a swimming bear as an illustrative intermediate in whale evolution.


You might want to learn about Dicty, at least at the high-school level, before dismissing it with such a silly hand wave. It doesn’t alternate generations in any way.

Exactly. It shows that multicellularity didn’t have to start out as obligate as Paul is claiming, just as an alternative life cycle.

Dicty does all of this aggregation and differentiation upon starvation just so that its spores can be blown a few millimeters away, where there might be food.

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“Sir, I have found you an argument; but I am not obliged to find you an understanding.” (Samuel Johnson, 1709-1784)

The problem of the origin of metazoan cell differentiation is well-established in the evo-devo literature (see the work of Rupert Riedl, Lewis Wolpert, Wallace Arthur, among others). It’s a waste of my time to spoon-feed basic concepts here. I’m sorry you don’t like videos, John, but the puzzle is laid out very clearly at the links above.

I am, however, genuinely interested (no sarcasm) to see how Dicty or a Dicty-type life history would illuminate the origin of cell differentiation in any animal. C. elegans provides a suitable case study, because we have a lot of data (cell lineages, genetics, and so on).

That’s it for me until something more interesting pops up in this thread.

I can just see you asking me, “How was my car GPS developed?” I would reply, “Well, it started off for use by the military,” and you’d cut me off with, “That’s irrelevant to the puzzle of GPS, because my question pertained only to the origin of automotive GPS!”

Not if reproduction is asexual.

So you don’t actually want to talk about anything and you refuse to explain anything. Hey, @jongarvey, since you have seen the video, will you take over and explain what Paul is talking (or refusing to talk) about?


Do you not realize that Wolpert himself worked on Dicty?

The problem is that you are ignoring basic concepts.

Where is Dicty mentioned in the video?

I find that hard to believe.

Actually, it isn’t suitable at all, because it is mosaic, not regulative (like Dicty and us), in its development. Mosaicism would come long after the evolution of multicellularity.

That may be why you don’t see how it could evolve; alternatively, you do, which is why you chose an outlying mosaic case and are misrepresenting it as the norm to fool people (maybe including yourself).

What kind of scientist flounces from a discussion of his own hypothesis-free proposal?

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One might also point out that even some unicellular protists produce gametes.

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Indeed. The bottom line is that there are living examples that violate pretty much every evolutionary sequence @pnelson claims would have been required.

His requirement that the initial multicellular state be mosaic is particularly ridiculous.

Paul, please note that I read your St. Denis essay. Predictably, it shows no understanding of regulatory vs. mosaic development. Why is that?

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That’s cute but, presumably, you’re not posting merely for your own entertainment? Seems to me you have some obligation of clarity if you wish for your arguments to be persuasive. Or at the very least understood.

But now you’ve run away with a vague handwave towards three author’s names. Does this shirt work with your “normal” audiences?


So you’re claiming that in the video, @pnelson literally addresses Dictyostelium and the difference between regulatory and mosaic development, completely justifying his assumption that the first metazoans had the latter?

In the time you’ve spent finding fault with a 2003 paper Paul started off the thread by apologising for, you could have checked for yourself.

If proper science is not done in videos, then it certainly isn’t done by second-guessing the impressions of people who’ve watched the videos you haven’t bothered to look at yourself: impressions solicited by other people who couldn’t be bothered to watch the video.

I see neither intellectual curiosity nor good faith in the responses on this thread. Maybe it’s an American thing.

That’s a cute quote, but it’s not relevant because you have not presented an argument here, just some unrelated claims and facts, none of which have any connection to your formula for ontogenetic depth.

There is an argument in your linked article, but that argument is based on the assumption that the evolution of an animal follows a similar path to its development. This is clear from your comment here about reproductive capability arising at the end of development; from several statements in your paper (most notably, “Those features disappear because the normal functional role of CEICP is end-directed, aiming towards the adult worm, and the adult worm doesn’t exist yet.”), and from your diagrams which show the path of evolution of C elegans as an increase in cell number.

Unfortunately, that argument is just a more sophisticated version of the ignorant question ‘How can a butterfly evolve from a caterpillar?’. It’s based on a fundamental misunderstanding of evolution. Animals didn’t evolve by an extension of their development from zygotes to adults. Animals actually evolved by alteration of the already existing development and reproduction cycle into something more complex than just grow then divide. There was no such point at which “the adult worm doesn’t exist yet”; at every point along that evolutionary path there was an animal which developed into an ‘adult’ form.

You had a chance to realise this when you said “Simpler’ animals, such as Trichoplax, with only a handful of cell types, actually possess many more cells than C. elegans” where you noted that complexity doesn’t actually correlate with cell number, and so it’s quite possible that the ancestors of C elegans had around a thousand cells (or even more) at maturity before the cellular differentiation pattern evolved. But you missed it.

It’s also clear that whatever your argument is supposed to be, your formula for ontogenetic depth isn’t part of it - because despite your claim that “The ontogenetic depth of a handful of extant animals … is known with precision.” I haven’t found a single case of you actually giving any such value.

Yes, it is. But that problem is unrelated to your problem, which is just a rehash of the ‘butterflies could evolve from caterpillars’ misunderstanding.

The spoon isn’t in the orientation you think it is.


Many thanks - that’s the counterexample I remembered, but not well enough to identify.