If I said that evolutionary theory was only neutral theory, everyone would howl. Especially if started to point to well know evidence for other mechanisms, as if that demonstrates evolutionary theory was failing.
I don’t execute such innane debate tactics so no one objects. I do not mistake the part for the whole.
Contrast that with Behe and the Dissent From Darwinism. In this case positive selection is equicovated as the whole of evolutionary science, this strawman is knocked down, and a victory dance ensues about how evolutionary science has been toppled.
One must be willfully blind not to see the difference.
Now, ironically, I’m being charged for misrepresenting the science by emphasizing well accepted non-Darwinian mechanisms. Silliness. Who could possibly take this seriously.
See my explanatory post. My notes and my memory were just fine - and my colloquialism was conscious. If I’d meant rhipidistians I’d have said so. Funny how you guys are so keen to correct perceived errors rather than be glad that someone explained the comment made to Eddie.
Neil, you’ll have heard the usual answer to that - “Such language is just a convenience.” But it would be better acknowledged, and maybe its reasons pondered.
Who here is trying to criticize modern evolutionary theory? Please try to focus on what is actually being argued. I for one would genuinely appreciate it.
“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.
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.
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.
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.
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.
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.
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.
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.
