Evolutionary Science, not Darwinism

Eddie wrote earlier:

“And Shapiro might be wrong to characterize all of current evolutionary theory as “neo-Darwinian”, but again, in context, it’s clear why he calls the self-engineering of the genome a “non-Darwinian” process. Behe uses the term “Darwinian” and “neo-Darwinian” in a certain way, and his objection to evolutionary theory are objections to neo-Darwinian thinking rather than to evolution in itself – but that is clear in context.”

There are people who are trying to claim that ID is true because Darwinism is false.

I’m not one of them.

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That reminds of when somebody argued (on usenet) that we should avoid all intentional and intensional language and do everything in FOPC (first order predicate calculus). So I asked him to post to usenet using FOPC. And I repeated that request several times. Of course, he never did, because it really isn’t possible.

Most of the time, it doesn’t matter that much. But in evolutionary biology, it does matter. A poor choice of intentional language will be picked up by creationists and used to attack evolution.

???

You should know that “rhipidistian” is an obsolete term referring to a paraphyletic assemblage of early sarcopterygians, none of them having anything to do with the origin of lungs, though some of them are fairly close relatives of lungfish.

@Mung

“Evolution” will always be the best term… especially if flawed versions of tge theory are intentionally excluded.

Conversely, “Darwinism” is a more parochial term… and was embraced before we even knew what DNA was about!

@mung… this trumps your issue definitively!

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Moved to new thread. Not my idea.

Well, always nice to know. I won’t attempt to get Wikipedia to update their page, but it may come in handy in another fifty years time when I next have any reason to consider the origins of the teleost swim bladder… though by that time, the taxa will have changed again, without a shadow of doubt. :grinning:

Just curious: what page?

Lungfish

Thanks. I didn’t know that “Rhipidistia” had been redefined. Using that definition, the term is not obsolete, but it doesn’t mean what you thought it did. And by any definition, rhipidistians have nothing to do with the origin of lungs. Nor do lungfish.

Was not the issue under discussion the origin of swim bladders?

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Both, really. You claimed that lungs evolved from swim bladders, I claimed that swim bladders evolved from lungs. Anyway, rhipidistians are relevant to neither. As you have noticed, swim bladders are a feature of actinopterygians, not sarcopterygians. And lungs are prior to both groups.

No, you’re wrong. I never claimed that - Eddie remembered that from Darwin, and I corrected him.

OK, now I’m lost. Where did you correct him? How?

Well, I’m not going to link to every post on this thread and the one to which my reply was hived off, but I will generously remind you of the sequence from memory - and give value-added notes.

Eddie mentioned swim bladders offhand in a post:

And you said he’d got it the wrong way round. He replied:

If I recall correctly, Darwin suggested that the lungs developed, or could have developed, from the swimming bladder. I think I’ve seen the suggestion elsewhere as well. So I wasn’t making the example up. However, I have no idea what the current thinking is on the evolution of lungs.

And he was right, because in the Origin of Species (ch VI, Section 5, p686 in my edition) Darwin writes:

The illustration of the swim-bladder in fishes is a good one, because it shows us clearly the highly important fact that an organ originally constructed for one purpose, namely flotation, may be converted into one for a widely different purpose, namely respiration. The swim-bladder has, also, been worked in as an accessory to the auditory organs of certain fishes. All physiologists admit that the swim-bladder is homologous, or “ideally similar” in position and structure with the lungs of the higher vertebrate animals: hence there is no reason to doubt that the swim- bladder has actually been converted into lungs, or an organ used exclusively for respiration.

According to this view it may be inferred that all vertebrate animals with true lungs are descended by ordinary generation from an ancient and unknown prototype which was furnished with a floating apparatus or swim-bladder.

I replied to Eddie that indeed I remembered from my distant school zoology that teleost swim bladders were then, at least, believed to have evolved from the lungs of early fish I termed “lungfish” for brevity, rather than lungs evolving from swim bladders, though I was in fact quite aware that these were primitive fish unconnected with the modern lungfish.

My A-level notes, which I still have, confirmed this memory, and I gave the 1968 version of the phylogeny of teleosts, throwing in the name of the only modern lunged descendant of their common ancestor to explain why that was the view.

I subsequently mined Wikipedia for the ancestry of the modern lungfish, since you were wrongly suggesting I’d claimed swim bladders came from them, a suggestion you later changed somehow to saying I’d been trying to explain the origin of vertebrate lungs.

All very simple, if one isn’t intent on proving every statement Eddie or I made to be in error. And even in 1968 I didn’t make crass errors in zoology, which is why I gained a Grade A, with Distinction in the scholarship examination.

Maybe better not to pick on minor and irrelevant perceived errors in the first place.

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That jives with what I remember reading on the subject. On a similar note, I remember reading cartilaginous skeletons in Chondrichthyes may have evolved from ancestors with bony skeletons. I think both instances are good reminders that evolutionary histories aren’t as simple as we sometimes think.

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At the risk of being misunderstood again, but following the interesting pursuit of “the history of phylogeny” I’ve checked my 1968 notes on that - my notes state both possibilities, and the accompanying tree, based remember entirely on fossil evidence and taxonomy at that time, has the Chondrichthyes diverging somewhere above the root of the placoderms, implying that bone loss is more likely than original cartilage. So I’ve never known any different!

Checking a modern phylogeny I see that, with some refinement, that’s still one story today, but that there is a long running controversy about whether they arose monophyletically from placoderms, or from pre-placoderms, or are polyphyletic. The final resolution doesn’t matter here as it doesn’t affect the discussion, and will no doubt change again.

However, it does confirm your point that “evolutionary histories aren’t as simple as we sometimes think.” That’s another way of saying that nested hierarchies nest in alternative ways, and that’s the one major thing I have learned since school, when it looked as if the tree of life was done and dusted apart from the details.

I’ve got into the habit, whenever a particular taxon comes to my attention either on a blog, in an article on in the garden, of checking out its phylogenetic origins. So far every single case has turned out to be disputed or uncertain, and the Chondrichthyes are no exception, so thanks for prompting me to look.

What else are internet discussion groups for? Anyway, while it is minor and irrelevant, it’s not just a “perceived error”. It’s a real error.

Clearly, I have trouble telling internet posters apart, as I didn’t notice that you had changed from Eddie to yourself. Sorry.

Regarding the point (a minor and irrelevant error):

  1. Darwin said it, and Darwin was wrong; not the only time.
  2. Lungs evolved prior to the split between Sarcopterygii and Actinopterygii, possibly much earlier. There’s a very well-preserved placoderm with what appear to be lungs.
  3. Your use of the term “lungfish” was ill-advised, as words do have meanings. Polypterus is definitely not a lungfish. And of course it’s not ancestral to other actinopterygians either.

Relationships among chondrichthyans, placoderms, and bony fish are currently still unclear. However, one should be clear on what “bony skeleton” means. There is, for example, a distinction between dermal bone and endochondral bone. The ancestors of sharks clearly had dermal bone, as did placoderms. But they probably didn’t have endochondral bone, and placoderms didn’t either. Same for the various groups of “agnathans” that preceded the jawed fish, though some of them had a third type, perichondral bone. Scales are a type of dermal bone, and sharks still have that.

Wow. You have bad luck in sampling. Most taxa are not disputed or uncertain. Of course long-extinct taxa are more difficult to place than living ones, but still the clear cases outnumber the doubtful ones.

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@swamidass has been vocal in reminding me that the nested hierarchies have noise, and it is a very good point to remember. Homoplasies, incomplete lineage sorting, and severe lack of data for deep nodes are all real things that scientists have to deal with and be cognizant of. If nothing else, gaps in our knowledge should excite us because those gaps are telling us we have new things to learn.

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A post was split to a new topic: Purpose in Science

I will find the link later, but related to this question, I noticed that PBS’s website described the convergence of the animals of South America and Australia simply as an example of natural selection “selecting” the same types of animals in two different instances. This seems right in line with the EES’s understanding of how the modern synthesis understands things and the explanation seems wholly inadequate to me.

What is everyone’s opinion on this chart from the EES?
https://extendedevolutionarysynthesis.com/about-the-ees/how-the-ees-differs-from-the-modern-synthesis/

It seems that an MS person might be fine with leaving the PBS explanation as is since it’s for a non-scientific audience. However, an EES person might insist that niche construction and developmental bias MUST be mentioned to explain this convergence because although an MS person would acknowledge these mechanisms, she he might not see them as crucial. An EES might see them as MORE crucial than selection.

It seems to me that the biggest difference between the MS and EES will show up when discussing how to teach evolution to high schoolers/non science persons.

For example, somewhere on here @swamidass said that Ken Miller’s presentation of evolution might come off as Neo-Darwinian because he was oversimplifying things. Yes! Exactly.

But if an EES person simplifies things, we might hear much more about developmental bias, niche construction, epigenetics, etc. because she would see these mechanisms as more crucial to the evolutionary process than would an MS person.

It seems that @sygarte is absolutely right. The difference between the MS and EES is one of emphasis. @Eddie @swamidass @Mung @jongarvey what are your thoughts?