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Author | Topic: Iridium Nightmare and Living Fossils | ||||||||||||||||||||||||
Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Oooh. Shred the creationist. My favorite game.
quote: I love it when a creationist tries to tell evolutionary biologists or paleontologists what the evidence indicates. Nothing like setting up a straw man to knock down. Wonder where the author got the idea that species only can’t persist relatively unchanged but according to evolutionary theories certainly not millions of years. ? Why not? Every evolutionary biology text written in the last 20 years talks about stasis and punctuated equilibrium. Most include examples even more startling than these few provided here. Trilobites persisted for around 200 million years. Unless you’re a specialist, the 6 orders of trilobites look pretty much the same. Ditto nautiloids. Fairy shrimp (Triops spp.) have been pretty much unchanged since the Silurian. Skunk cabbage (Symplocarpus foetidus) have been evolutionarily stable for about 8 million years. The list goes on. At the opposite extreme, of course, you have lineages that speciate very rapidly, like the cichlids of Lake Victoria in East Africa ( 400+ species appearing in less than 12,000 years.) We even have species that are trapped at the moment of speciation — c.f. the fascinating natural history of Darwin’s 14th finch, Pinaroloxias inornata, which because of a near-total lack of competition has adapted to every conceivable bird-niche on the island. There are finches that eat snails and small arthropods, seed eaters, nectarivores, fructivores, etc. However, they remain freely interbreeding, and no morphological changes have taken place (beak size, for instance, is intermediate between finch and warbler). Each individual juvenile of this species picks an adult to emulate — even the adults of a different species. It follows the behavior patterns of the particular adult for a few weeks, or even for its entire life. Why haven’t these myriad behavior patterns developed into distinct, non-interbreeding new species? The island is too small — there is insufficient room for these birds to bud into non-interbreeding populations. To make a long story shorter, rates of evolution are highly variable. Some lineages seem to speciate very rapidly, others remain relatively unchanged for literally millions of years.
quote: You won’t find a single working ecologist or evolutionist who holds to this explanation for evolutionary stasis. Another creationist attempt to impute their own ignorance to scientists. Let’s take a look at evolutionary stasis. There are really two related issues here. In the first place, if I might be forgiven an anthropomorphism, natural selection tends to be conservative (if it ain’t broke, don’t fix it). Once a population or species becomes adapted to its environment, natural selection will tend to weed out any misfits. There will, of course, be variation, but it will tend to vary around a mean frequency. This evolutionary stable strategy is difficult to upset unless the environmental variables change. When an ESS experiences disequilibrium, the population either adapts (by NS favoring the expression of all those suppressed alleles), moves (habitat tracking), or goes extinct (crash). In the latter two cases, we’ll see an abrupt disappearance of a species from a particular geological site. The other related issue is the fact that, in an environment that doesn’t change much over very loooong periods of time, an ESS — once achieved — will favor those populations best adapted to that environment. In places like the ocean, where conditions are pretty invariant, this apparent stasis can last millions of years — basically until something relatively drastic occurs to cause change. I think it is significant, in this context, to remember that Gould and Eldridge were studying marine organisms when they came up with their theory of punctuated equilibrium (snails and trilobites, respectively). Once a stasis situation changes, radiation and adaptation occur rapidly, as natural selection operates on the remaining population — permitting radiation into new niches created by the change in environment, and favoring those traits that are more adapted. (One of the things we see is that often it’s the non-specialist organism that is favored. The exquisitely fit organism, near-perfectly adapted to the existing environment over eons, simply can’t change quickly enough to survive.) Finally, it needs to be remembered that once a species or lineage has acquired an effective isolating mechanism of some kind, it may NOT materially change over millions of years — no reason for it to. All the species with which the living fossils (what a silly term — like saying living rock) shared their original ecosystems have either changed beyond recognition OR gone extinct. Why the genotype of a particular species like the horseshoe crab (Limulus) managed to maintain itself without substantial change is unknown — at this time — but there’s a whole subspecialty of evolutionary developmental biology that is working on the issue. My current favorite hypothesis is a combination of normalizing selection (which also operates on fast speciating lineages) and an as-yet-unidentified inherent property of certain genotypes that allows them to resist mutation — the key element in producing variability in a population. Please note: resist may indicate either very efficient error correction at the DNA level, or an extremely delicate organism that simply is unable to survive a normal level of mutation hence MORE vulnerable to negative selection, or something I haven’t thought of yet. It doesn’t mean there’s something teleological going on here
quote: Actually, our little shrimp may have survived three — Permian, Triassic and Cretaceous — mass extinction events. My question is, so what? Most major classes had survivors — even of the incredibly devastating Permian extinction which almost cancelled the entire experiment in life of this planet. Crocodiles* survived the Alvarez event? 80% of their relatives didn’t. In all mass extinctions, there appears to be a very strong element of chance that allows some lineages to survive relatively intact, while others disappear forever. Sarcosuchus imperator[/i], the entire family Atoposauridae, and Simosuchus clarkii are all extinct crocodilians. There are currently 23 living species — which ones are you claiming have survived since before the K-T event?) The obvious follow-up question:
quote: The answer goes back to differential rates of speciation among different lineages. Increased evolutionary tempo is somewhat misleading. It took nearly 20 million years for biodiversity to recover from the K-T Alvarez event, nearly 100 million for the recovery following the Permian and Triassic events (since the T-J mass extinction occurred while the planet was still recovering from the P-T event). Life was severely impoverished for a very long time following the major catastrophes. In each case, organisms that were superlatively evolved and dominant disappeared, others survived. Of the survivors, differential evolutionary rates explain why some lineages were able to radiate rapidly, whereas others remained relatively unchanged.
quote: Errr, no. See above.
quote: Except that genetic drift is only evident among small populations with no gene flow or immigration. There’s also non-random mate and kin selection, intraspecific competition, etc. The only people perplexed are creationists who haven’t bothered to try and understand evolution.
quote: What’s your point? I already covered this.
quote: Of course, all the other 13 million extant species changed, but why bother inserting facts into a good polemic? Okay, so we have maybe a dozen species overall out of millions whose morphology hasn’t significantly changed for millions of years. This is somehow supposed to refute evolution? Creationists really need to get some new arguments.
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Ahh, the typical creationist handwave — unable to refute the evidence provided — or even understand it - they merely wave it away.
quote: It is quite apparent that you didn’t even read the post, if this is the only response you can come up with. I merely refuted point-by-point everything you (or whoever) wrote in that polemic. It doesn’t help your case to simply ignore the counterarguments.
quote: Au contraire, I very carefully explained evolutionary stasis, using the mechanisms we observe in living ecosystems. Unless you’re able to show how evolutionary biologists, paleontologists, ecologists, etc are wrong, all you’ve succeeded in doing is making baseless assertions.
quote: And that’s the major problem with creationists — unable to counter the weight of evidence on the side of modern science, they resort to argument from incredulity and pseudo-intellectual appeals to ignorance. I assume your target audience with that little screed are those who have little grounding in or understanding of science?
quote: Okay, I’ll play. Let’s take a look at those three reasons.
quote: Where did you come up with this assertion? Care to provide any evidence to back it up? I’d be especially interested in where you get the concept of normal mutation path. I noted normalizing selection (look up the words if you don’t understand what this means) is a well-established evolutionary mechanism. RM&NS can quite easily maintain the status quo in either lineages or individual species. Since variables such as source-sink equilibrium, turnover pulse, ESS, coordinated stasis, CAS, differential selection pressures, etc, all effect the rate of evolutionary change, it is quite evident that mutation is NOT the only — or even the principal — mechanism for mean phenotypical change in a population. All mutation does is generate the individual variability upon which natural selection operates. Normalizing selection quite easily eliminates both deleterious and beneficial mutations. For example, paleontologists have documented eight successive intervals of coordinated stasis in the Middle Paleozoic of the eastern US (total time about 45-55 million years). During these intervals, lasting roughly 5-7 million years each, between 70-85% of the extant species are present throughout the interval. However, only about 20% make it unchanged through to the next interval. The pattern that is observed in nature — rather than the pattern you WANT to observe - is great ecological stability (with concurrent evolutionary stability in both plant and animal species), followed by disruption/discontinuity of ecosystems with high rates of extinction, followed by rapid radiation and proliferation of descendant species. Mass extinctions, because of the extreme global disruption, are simply this pattern writ large.
quote: This assertion is simply wrong. Genetic drift only effects small, isolated populations. Not large, heterogenous, globally occurring populations such as Limulus. Genetic drift also does not normally produce major phenotypical change — although it can produce both new species and phyletic change within a particular lineage. This brings me to another point. You are also conflating two completely different concepts here and in your main article. You are confusing phyletic evolution (change in the characteristics of a single lineage — which is what you are arguing against) with speciation. Simply because a single lineage does not significantly change over time, doesn’t mean it didn’t give rise to other species. Your strawman here is the dual implicit claim that orthogenesis is somehow a foundation of evolutionary theory (not for the last 100 years, at least quote: What’s your point? The tempo DID increase — just as it did after each mass extinction event. Just as it does at the local level following local extinctions or environmental change. If you read my post, you’d know that. Mammalian radiation, for example, skyrocketed after the K-T extinction (if you consider 20 million years skyrocketing). This has ABSOLUTELY NOTHING to do with the persistence of certain lineages. Just what point are you trying to prove?
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Hi Fedmahn. Thanks for the heads up. I was already getting that impression - note the failure to respond substantively to any of my points in my first two posts. OTOH, this tactic tends to backfire on boards with a lot of lurkers. After all, I never expected to convince ksc of anything. As long as it can be shown conclusively that the particular creationist either doesn't have a clue or how his/her arguments fail to hold water - both of which have been accomplished pretty much in this case, IMO - then the lurkers get an education. The creationist of course simply becomes petulant and ultimately retires from the field, often retreating to another board to claim victory.
Anyway, thanks for the heads up. I had never heard of karl - although you aren't the only one to mention him. I'm about done on this thread anyway.
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Actually, it turns out there was one point that I neglected. Concerning coordinated stasis:
quote: Just to show I'm not making it up, see for example C. Brett and G. Baird 1995, "Coordinated Stasis and Evolutionary Ecology of Silurian to Middle Devonian Faunas in the Appalachian Basin", excerpted from ppg. 285-315, R. Ansley and D.H Erwin (eds) 1995, "Speciation in the Fossil Record". Not that ksc will actually look up the reference, but others with access to a good library might find the entire article interesting, not to mention the other articles in Ansley/Erwin's book.
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
And it would probably be even more enjoyable for us if you could respond substantively to anything anyone has posted in rebuttal to your bald assertions. Care to refute ESS, the stabilizing influence of CAS, or the hypothesis of coordinated stasis as an explanation, or even simple normalizing selection? Care to address the issue of phyletic evolution vs speciation? Care to address the refutation of your claim that orthogenesis is a foundational principle of ToE? Or anything else we've written...
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Okay, ksc. Last chance. You claim to have answered everyone’s points. Guess we should take a moment to look over what’s really happened
Quoted sections (Quetzal) are from post #10 on this thread, quoted sections from ksc are from his alleged response on message #11, with current additions.
quote: What on earth are "evo facts"? Is this a textbook, article, journal, website, what? "No status quo" is a bald assertion on your part with absolutely no evidence. You call this responding? You have not shown that natural selection cannot maintain equilibrium. The fact is that status quo is one of the three possible outcomes to natural selection:
I hope you note from this graphic that phenotypical stability is expected as one of the normal outcomes of natural selection. Now it is incumbent upon YOU to refute this - since it directly challenges your opening assertion that "living fossils must evolve". Provide references.
quote: On the contrary, you have been provided the precise mechanisms how such stasis is maintained over quite a long period of time. Perhaps you’d care to show why these mechanisms were incapable of maintaining species relatively unchanged over evolutionary time scales? Your response is another hand-wave. Perhaps you don’t know enough about evolutionary theory and its mechanisms to respond (in which case your OP becomes pretty obviously erroneous)?
quote: References provided in message # 20 in this thread. Would you care to provide specific evidence that shows a world-wide flood actually occurred? Also, evidence that the fossil record — which extends backwards in time for ~3.5 billion years — indicates that all these organisms were contemporaneous? Of course, you’ll be able to cite specific references?
quote: Restating your assertion without addressing my points does not constitute a rebuttal. Care to respond concerning your obvious error on genetic drift? Not to mention the rest of the errors I pointed out.
quote: Another restatement of your original bald assertion. Again, you have failed to address the points refuting your post. Try again. I would say that Percy is absolutely correct. You have neither debated in good faith NOR provided any evidence or argument or answer to anything I — or anyone else - wrote. My suggestion would be to substantively address what has been presented refuting your spurious arguments, or go play with yourself somewhere else.
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
This discussion is getting surreal.
ksc: Why are you continuing to state that so-called living fossils are somehow a refutation of biology? Even the references you provided actually speak AGAINST this theory (with the exception of Plaisted, who I'll get to in a moment). You literally don't have any idea what you're cutting-and-pasting, do you? Let's take a look: 1. You reject Theobald's well-referenced article, claiming he provides no evidence. Yet he provides copious examples of every assertion he makes throughout that essay. One of the key points you missed out on is from the last line of the paragraph you quoted: "In fact, paleontological studies indicate the average longevity of 21 living families of vertebrates is approximately 70 million years. (emphasis added)" The point here is that higher taxonomic rankings - in this case families - are even MORE stable over time than individual species. Mayr makes a similar point about mass extinctions: higher taxonomic classifications are conserved (example: whereas some 75-80% of all extant species went extinct at the end of the Cretaceous, only 16% of all extant families went extinct. This is purely an artifact of the system of classification we use. Mayr 2001, "What Evolution Is", pg 202.) Once again, we have actual evolutionary biologists predicting that stasis IS OBSERVED - and why. It isn't some strange new phenomenon that somehow falsifies evolution. 2. Your reference from the creationist Plaisted is interesting. No surprise that he uses stasis as somehow refuting evolution. Is this where you got your idea in the first place? Talk about not providing any evidence whatsoever. Plaisted's entire essay is utterly devoid of evidence - and constitutes at best philosophical musings. Plaisted in general probably isn't all that reliable - and not because he's a creationist. He has published numerous essays which have been shown to be completely erroneous (see, for example, his mistakes on retroposons, refuted by Plagarized Errors and Molecular Genetics. 3. The Mayr and Gliedman quotes merely point out that evolutionary stasis is not completely understood. No kidding. Not much support for your claim that organisms MUST evolve. BTW: that website was hysterical. Thanks for the link. 4. Korthoff quoting Matt Ridley: "Natural selection is described as a theory of evolution, and indeed it is one, but it is a theory of non-evolution too." Ooops, you probably shouldn't have referenced this one. Ridley is quite clearly stating that natural selection ALSO explains persistence of "living fossils", conservation of genetic material, etc. Sort of provides additional refutation to your claim that organisms MUST evolve, doesn't it... 5. Your link referencing Eldredge didn't work, so I can't speak to the context or the original sources. Although to me the bit on Eldredge sounds like something from one of his pro-PE anti-darwinian- strict-adaptationist essays. Suggest fixing the link so we can see what was actually written, or at least the references the author of your cut-and-paste actually used. On to dueling graphics: quote: So? Actually, your graphic ONLY showed the action of normalizing or stabilizing selection. You'll note that the variation is in fact around the mean. Like I said.
quote: Right, stabilizing selection works to eliminate the extremes in variation. Meaning that there would be a tendancy in this type of NS to maintain the relative status quo - in the case of coelocanths, this means that they might have gotten bigger, as was pointed out, but that the population mean is generally stable. Oops, you just refuted your own assertion. Timescales DON'T matter!!!! Try again.
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Quetzal Member (Idle past 5901 days) Posts: 3228 Joined: |
Hi Andya. Welcome. Here's a link to more information on Latimeria menadoensis. The article is interesting because it mentions the Latimeria habitat preferences are identical between the two species, but they are genetically distinct. As though more info were needed that ksc was talking out his, err, fundament.
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