Coelacanth evolution

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I was reminded of one of the more comical, but persistent misconceptions by creationists in a thread on Internet Infidels, on The Coelacanth. Try doing a google search for “coelacanth creation" and be amazed at the volume of ignorance pumped out on this subject. I've also run across a more recent example of the misrepresentation of the coelacanth that I'll mention later … this poor fish has a long history of abuse by creationists, though, so here's a brief rundown of wacky creationist interpretations.

Crystal Clear Creation: Unlock the secrets of nature, wildlife, the world, from a creationist, Christian, non-evolution perspective.

Evolutionary scientists used to think that amphibians evolved from a group of fishes that included the coelacanth, which was known only from fossils. But they dropped this idea when living coelacanths were found from 1938 showing no evidence of evolution from the oldest fossil coelacanths to the living examples.The evidence from the coelacanth is good evidence for creation, for it shows that DNA, the genetic code, has remained stable throughout time.

Coelacanths, living fossils, and evolution

The fossil record, with its lack of intermediate forms and its unchanging biota such as the coelacanth, falsifies evolution.

The Five Crises in Evolutionary Theory

Some animals and plants have remained unchanged for literally hundreds of millions of years. These “living fossils” can be more embarrassing for the evolutionist than they often care to admit. One creature in particular, the coelacanth, is very instructive. The first live coelacanth was found off the coast of Madagascar in 1938. Coelacanths were thought to be extinct for 100 million years. But most evolutionists saw this discovery as a great opportunity to glimpse the workings of a tetrapod ancestor. Coelacanths resemble the proposed ancestors of amphibians. It was hoped that some clues could be derived from the modern coelacanth of just how a fish became preadapted for life on land, because not only was there a complete skeleton, but a full set of internal organs to boot. The results of the study were very disappointing. The modern coelacanth showed no evidence of internal organs preadapted for use in a terrestrial environment. The coelacanth is a fish--nothing more, nothing less. Its bony fins are used as exceptionally well-designed paddles for changing direction in deep-sea environment, not the proto-limbs of future amphibians.

Darwinism refuted:

Living coelacanths revealed how groundless the speculation regarding them was. Contrary to what had been claimed, coelacanths had neither a primitive lung nor a large brain. The organ that evolutionist researchers had proposed as a primitive lung turned out to be nothing but a fat-filled swimbladder. Furthermore, the coelacanth, which was introduced as “a reptile candidate preparing to pass from sea to land,” was in reality a fish that lived in the depths of the oceans and never approached nearer than 180 meters from the surface.

All of the above sites and quotes are odious nonsense. Any time a creationist tries to tell you that “living fossils” disprove evolution, you know that he or she a) doesn’t understand the theory of evolution at all, and b) hasn’t honestly looked at the evidence they think they are presenting. They might as well get the word “Idiot” tattooed into their forehead; as a signifier of their intellectual prowess, it would be just as accurate. They all make several gross errors.

"Unchanging forms” refute evolution. Not quite true. A species that exhibited no variation at all, and that showed no change over time, not even neutral molecular differences, would be a major puzzler for biology. No such thing has ever been observed. On the other hand, gross structural stasis over a long period of time is no problem for evolution. One thing even many biology students have some difficulty grasping is that selection is a conservative force; it tends to limit variation to the narrower domain of the viable and the competitive.

Coelacanths are unchanging forms that show no evidence of evolution. Read the quotes above: the creationists can’t even get their stories straight. They repeatedly claim that the coelacanth is “stable” and “unchanging”, but then they turn around and point out huge differences between what we know of coelacanths in the fossil record and modern forms: they live in different environments with remarkably different physiology. Which is it? Are they unchanging or are they radically changed?

The answer is that modern coelacanths are specialized remnants of a once diverse and widespread group. They have changed extensively over hundreds of millions of years, as would be expected, and this once widely successful and branched family has been pruned back to just a few twigs lurking in relatively inaccessible locations. Here, for instance, are a few fossil examples of ancient coelacanth diversity (Clack, 2002):

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A. Macropomoides orientalis, from the late Cretaceous.
B. Rhabdoderma elegans, late Carboniferous.
C. Allenypterus montanus, early Carboniferous.

"Coelacanth" is a term that refers to an entire order of fish, the Coelacanthiformes. The modern coelacanths are of the genus Latimeria, and none of the ancient fish belong to that genus—it ought to be fairly obvious that Latimeria is clearly distinct from any of the fossil forms if it was assigned to a unique genus. The brilliant creationists who point to Latimeria and claim that it is an example of an unchanging form might want to reconsider; would they also point to a random member of the primate order, say a howler monkey, and announce that it is obvious that all primates for all of their history have been identical?

Scientists haven’t been disappointed by the coelacanth at all. It’s wonderful to have at least a few representatives of a family once thought to be extinct that are still around. Personally, one thing I’d like to know more about is that fascinating limb duplication they exhibit.  They have a second dorsal and anal fin that each have a partial girdle structure—there’s an interesting story in molecular development in there, I’m sure.

(By the way, the web isn’t entirely a morass of inanities about coelacanth evolution. Wesley Elsberry, Mark Isaak, and Don Lindsay all say eminently sensible things on the subject...but then, they aren’t creationists.)


Clack, J (2002) Gaining Ground: the Origin and Evolution of Tetrapods. Indiana University Press, Bloomington.

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If the DNA is unchanged from the fossil ancestors, how did these people extract DNA from fossils? Did the DNA molecules fossilize into rocks? Boy, I'd like to see that!

Oh, there are so many things to say...

First, regarding this from one of the quotes:

The first live coelacanth was found off the coast of Madagascar in 1938.

The so-called "first coelocanth" was not from Madagascar. It was South Africa. Of course, coelocanths were fished by people in Madagascar for decades before being "discovered."

PZ: selection is a conservative force; it tends to limit variation to the narrower domain of the viable and the competitive. ... indeed, selection by very definition always limits variation.

Which brings us to a key point that the creationists get wrong, as you've said, but I want to say it again and again, and while I'm at it blame evolutionary biologists a little bit too: While it is true that latimeria is a different genus than the fossil coelocanth, there are forms that persist for very long periods of time, a few of which are of course alive today (and that would be true for any point in time in metazoan history).

For example, a fish in some ways cooler than the Coelocanth is Amia (Amiiformes). We Minnesotans occassionally catch them, and here they are known as "bowfins" or "dogfish." There are extinct members of this genus from the paleocene (but I can't swear to what they look like) and the genus Nipponamia also does not look all that different. Overall they seem less diverse in morphology than the Coelocanths

These fish are cool because when they are incorporated in the phylogeny of fishes, they demonstrate that living bony fish evolved from a lunged-ancestor. Which, of course, should drive the creationists nuts, becuase this means that evolutionists not only have it all wrong, but they have it ALL wrong because these fish evolved BACKWARDS. Only an intelligent designer would ever think of that!

OK, so here is where i'm going to blame the evolutionary biologists a bit here: Evolution means many things, and thus many "definitions" or discussions of evolution leave out one or another of these various things evolution can mean. Many preliminary discussions or introductory comments about evolution talk about change, and about mechanisms for change (NS vs drift, etc.). But one of the most powerful and amazing forces of evolution is stasis.

If we don't put stasis up front, then evolution means change to a lot of people, and thus it is easier to make the argument that non-change in non evolution, and all those other silly things creationists have in their bag of lies.

Morphological similarity is commonly misconceived as evidence for the absence of evolution. Nucleotide sequences of Comoran coelacanths differ substantially from those of Indonesian coelacanths.

correction: Stasis is not a force. Natural Selection is the most important force in generating stasis. Stasis is the pattern, nat sel is the process.

Sorry 'bout that.

Yeah, and then the creationists turn around and whimper that evolution means both change and non-change, and therefore we're trying to have it both ways.

What they miss is that the real world does contain examples of both change and stasis, and we need explanations (other than a god's whimsy) and mechanisms that can accommodate both. Theories that explain one but not the other are not useful.

... right! And another thing! What is "change"? There are organisms that all look exactly the same to us primates yet are not even closely related (like those large-leaved dentist-office plants ... virtually identical forms only distantly related). I see a few different species of Amia, and they all look pretty much the same, but to another Amia, they may be very different.

By the way, I should have mentioned this: Don't eat the Amia. There is no known way to make them taste good. I hear that's a common property of living fossils. Probably the reason they're not evolving any more ... they're in a good place, why move.

Thanks for posting this and clearing up the status of Coelacanth in my mind. I thought they were just a family, and I've never seen pictures of other genera before.

My point of view is that when conditions are stable, they keeps organisms on the same evolution evolutionary path, just as gravity keeps a cat walking in a straight line on a tall fence. Any deviation is punished by natural consequences. When conditions vary, it's as if the cat reaches the end of the fence and can scamper off in any direction....

Sort of but the cat is trying to stay on the fence, and this may support teleological thinking (the cat is being teleological, in a sense). Maybe more like a snake slithering in a steeply sided gutter...

(being chased by a cat, which here represents time.)

Ma gave me a book about the coelacanth back when I was in grade school. I forget the exact year, '58-'60 I guess. Nevertheless I have a distinct memory of the import of that book. Being told about a fish that had been considered dead for a jillion years and that then had been documented as currently extant made an instant and lasting impression. To wit: the notion that it was gone was wrong.

That's all. Live (and especially observe details and consider them) and learn. Which is much more than can be said by those in desperate search for justification of assumptions made (or passed down to them) without observing what actually happens.

I wonder what the fish might say about this if it could . . . Maybe "I was here, I left and then I returned". Very similar to the crux of current mysticism.

By Crudely Wrott (not verified) on 11 Mar 2007 #permalink

Ma gave me a book about the coelacanth back when I was in grade school. I forget the exact year, '58-'60 I guess.

Don't know if it's the same one, but the book that made such an impression on me was "Search for a Living Fossil". I got it a few years after it came out in 1963--maybe '67 or '68, and read and re-read it many times. I loved that book and that fish!

Oh, geez. The creationists really don't know crap about biology if they think that the coelacanth's the only animal that "hasn't changed that much" over the eons. It's not even the only fish about which that can be said -- look at the shark, for Pete's sake!

As you say modern Coelacanths aren't that closely related to their fossil counterparts. Unfortunately because of the depth that modern coelacanths live at the most closely related fossil ancestors would likely be burried somewhere off shore where paleontologists don't yet have the technology needed to get at them. Sadly, this is true for a lot of marine fossils, those that we can find on land are often from areas that had previously been shallow inland seas (or other shallow bodies of water), there is relatively little data on what might have lived in the open ocean. The coelacanths currently known from the fossil record are all shallow water, estuarine or river species whose remains can be found on land. Why does this matter? Well Latimaria is adapted for deep water, of course it wouldn't have useless things like lungs. Shallow water species, I don't know, some might have had lungs (points at lungfish, it's not exactly unheard of for fish to have functional lungs) or they might not have. The truth is that while scientists use to think that the coelacanth was the most probable ancestor for tetrapods (due in no small part to the structure of its fins) it is now believed that, no, they weren't.

With the comment about living fossils tasting bad - it's called urea, it's the same stuff in pee. I forget at the moment exactly why it's beneficial, bad taste aside.

This is very timely as I've just finished reading Samantha Weinberg's book Search for the Coelacanth. Good stuff!

By Silmarillion (not verified) on 11 Mar 2007 #permalink

I just finished a three part series on deep sea living fossils (including coelacanths) on my own blog so was very happy to see this posting. They are amazing and unique creatures of great scientific importance so it is frustrating to see them used to drive misconceptions.

(By the way, the web isn't entirely a morass of inanities about coelacanth evolution. Wesley Elsberry, Mark Isaak, and Don Lindsay all say eminently sensible things on the subject...but then, they aren't creationists.)

See also Martin Brazeau on the Tiktaalik/Coelacanth transitional arguments screwed up by the creationists.

Maybe more like a snake slithering in a steeply sided gutter...

Once you observe stasis, it is a realistic change, namely zero change. One problem is that people thinks in dualistic terms by nature, another is that consequently colloquial language supports that. But I agree, it is a good idea to point these things out.

By Torbjörn Larsson (not verified) on 12 Mar 2007 #permalink

I think these morons get thier preconceptions of evolution from playing EVO: The Search For Eden. (yes, I still have my Super NES hooked up. Don't laugh!)

By Laser Potato (not verified) on 12 Mar 2007 #permalink

No, don't look at the sharks for an example of extreme stasis. If you include any Devonian chondrichthyan in "sharks", then the rays are sharks, too. Even without them (and the angel sharks and the sawfishes etc.) we have three separate lineages of large plankton-eaters, plenty of shell-crackers, and so on among sharks.

Phylogenetic tree of Chondrichthyes (several pages!)

Phylogenetic tree of Actinistia (two pages!) Coelacanth diversity, while I am at it. The misspelled Megalocoelacanthus was a 3 m long plankton-eater last time I checked.

Lungs, incidentally, are normal for bony fishes; unless secondarily lost, they are present. Most ray-finned fishes have turned them into the swim bladder (on, it seems, just two occasions!), and Latimeria has filled them with fat because a gas-filled cavity would be crushed in the deep sea.

By David Marjanović (not verified) on 13 Mar 2007 #permalink

Maybe more like a snake slithering in a steeply sided gutter...

Once you observe stasis, it is a realistic change, namely zero change. One problem is that people thinks in dualistic terms by nature, another is that consequently colloquial language supports that. But I agree, it is a good idea to point these things out.

By Torbjörn Larsson (not verified) on 12 Mar 2007 #permalink

No, don't look at the sharks for an example of extreme stasis. If you include any Devonian chondrichthyan in "sharks", then the rays are sharks, too. Even without them (and the angel sharks and the sawfishes etc.) we have three separate lineages of large plankton-eaters, plenty of shell-crackers, and so on among sharks.

Phylogenetic tree of Chondrichthyes (several pages!)

Phylogenetic tree of Actinistia (two pages!) Coelacanth diversity, while I am at it. The misspelled Megalocoelacanthus was a 3 m long plankton-eater last time I checked.

Lungs, incidentally, are normal for bony fishes; unless secondarily lost, they are present. Most ray-finned fishes have turned them into the swim bladder (on, it seems, just two occasions!), and Latimeria has filled them with fat because a gas-filled cavity would be crushed in the deep sea.

By David Marjanović (not verified) on 13 Mar 2007 #permalink