nested heirarchies as evidence against darwinian evolution

That's interesting, but I don't see the finalising of a process that had already started in a common ancestor as non-superficial. The link I gave earlier described an earlier creature with some monotreme characteristics that was half-way to the mammalian ear. The science articles, unlike the page you linked to, describe the possible convergent stage in the ear evolution as only being the final movement of the bones.There's another point that occurred to me while reading the article from the University of Chicago Hospitals link at the bottom of the page. That monotreme does not have to be a direct ancestor of the ones we see today, but could be an extinct branch.The early mammals would have all been monotremes, and there could have been a number of branches. If breast feeding comes first, then the modern ear, then the placentals, the monotremes we see today could have branched off from our line when we were both "modern ear" monotremes, but the fossil described, before the finalisation of the ear development, meaning that no convergent evolution was necessary.I'm interested in that period of evolution, anyway, so I'll try and find out more about it.As for the site you linked to, we can see what kind of source you pick up your arguments from incredulity from!

It appears to me that you're working very hard at not understanding the answers.There won't be a lot of back and forth member/moderator posting. I haven't seen threads crumble into bits so fast since you were last here. Either threads you participate in begin to resemble constructive dialogue, or you'll be gone. I don't know how you're going to do this, but it's your problem, not mine.To everyone else:I again urge you, if you would like Randman to remain here, help the threads he participates in maintain a constructive dialogue.

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--	Percy
	EvC Forum Director

You and someone else have been saying this, and it would probably be helpful if we could establish the degree to which science accepts this view at the current time. A bit of Googling seems to indicate that the origin of almost all, if not all, of the animal phyla originated at the Cambrian, with a sprinkling of speculation that they may have originated earlier during a period when most creatures had soft body parts that don't often fossilize.Can we get to bottom of why the different viewpoints on this?--Percy

So, you'd like an animal that does not have a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail, to develop those things for the second time in the history of the earth? Would you like it to start out as exactly the same creature as the ancestor of the first chordate in exactly the same environment, and to receive exactly the same mutations and selection pressure?For this to happen would certainly be evidence of an intelligent designer. In evolution, that level of coincidence would be impossible.I think that your problem is that you're taking the word phyla to mean too literally a basic body plan rather then a classification by ancestry which is identifiable by the analysis of internal features, or the relics of them.So, you seem to be asking "why have no new body plans developed in the last 500 million years", when in fact, they have.If you look in the chordate subphylum Vertebrata, you can see animals as diverse in body plan as elephants, humming birds, snakes, goldfish, and us. So, do you really think that evolution isn't doing new "body plans".These are just classified in the same subphylum because they descended from the first vertebrate chordate, and before that, from the first chordate. They show at least traces of the chordate characteristics.And that first chordate probably had more characteristics in common with other animals that are the ancestors of other phyla than it does with many of its descendants. They were all small sea dwellers. All it was is a specific animal that produced a lot of descendant species, just like in later times the first fish, or the first mammal, or the first primate did.There's no reason why any of those specific "firsts" should evolve again. As at least one person on the thread has mentioned, your view of this sounds like the naivest sort of creationist question like "why don't the other apes evolve into us".

I believe the question is why did invertebrates not show much change anymore after one population gave rise to vertebrates.?Why couldn't another population give rise to something else and eventually become drastically different? The only change since this 'event' were very minor evolutionary changes..
Similarly, how is it that the ancestor of Man and Chimpanzee is very different from Man and not so different from the modern chimpanzee? Why could not another population of apes evolve from the chimpanzee? Why is it that the parent population has not changed much but is still around?
Why could not another population of fish give rise to another type of land animal - perhaps with different types of adaptations than amphibians?I think this is the gist of the main question? Why is the parent population still virtually unchanged, still around and not able to give rise to anything new save for that ONE time?I hope there is an explanation for this because I believe I understood evolution quite well and simply assumed that there was not an available niche for the animal to branch off again. But I don't think this is a sufficient explanation.

The invertebrates are successful as they are. Becoming a vertebrate or anything dramatically different isn't an inevitable route of evolution. The chimps aren't our parent population, but we share a common ancestor. However, you may be right in suggesting that they're more similar to the common ancestor, and part of the reason for that is that they may have stayed in the original environment, whereas our group moved out and adapted to new circumstances. We may also have received specific important changes in the genome that stimulated change that they did not receive.And of course another population of apes could evolve from the chimpanzee in the future, and indeed, there are already considerable differences between the chimps and bonobos. Fish aren't dying to be land animals, obviously, and there's no reason why that should happen regularly, although it could happen again. But there now being so many predators on land to welcome clumsy walkers on leg like fins might be a factor that goes against it happening again.The arthropods moved on shore as well, so it has happened twice. Successful creatures tend to stay as they are, and natural selection to act as a conservative force unless they find themselves in new environments. Of all the tens of thousands of fish species, only one came ashore, and of all the mammals, only the whale/dolphin ancestor made the complete move back to the sea. And simple creatures are not trying to get more complicated, either, it just happens to the occasional group.

indeed -- even after evolving some hard parts, some invertebrates have secondarily lost their supportive structures. for instance, there's quite a good advantage that the octopus has in its soft-bodied flexibility. teuthids and octopodes in fact evolved from animals that sported hard shells. at least twice. catfish routinely come up on land for food or cross small land barriers to journey to other bodies of water, and they're more or less unrelated to the lobe-finnded fish that gave rise to tetrapods. i think it happened a couple of times in arthropoda too, but arthropod evolution never really tickled my fancy much.

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Lith is on the case.He will post the answers tomorrow.(I am too lazy to look up all 33 phyla and their dates of origins.)Lith has all 33 at the tips of his fingers, but his reference book is at work.Til tomorrow!Tho I can't say I think it will do much good.When Rand finally admitted that vertebrates are not a phylum, he brushed it off with "Whatever." and repeated for the umpteenth time "But why aren't there new phyla in the last 500 million years?"I am taking wagers. How many are willing to bet that Rand's response to the emergence of different phyla after the Cambrian explosion is:"Why aren't there new phyla after XX million years then?" (XX = date of last phylum's emergence.)It's a "transitional fossil" type problem.When a creo is presented with a transitional between -- let's say fish and land animal -- the inevitable response is:"Where is the transitional fossil between fish and Tiktaalik and between Tiktaalik and land animal then?"It's a never ending battle.

i'm half thinking about posting images of each and every cambrian phylum. their similarities are rather startling -- posts by randman make it seem like we're talking about whole bodyplans popping into existence in the cambrian explosion and nothing new has happened since.we're really talking about thirty three different kinds of worms. {edit: okay, not all of them are worms, but the vast majority of them are. look it up}it's just that it happens that the minor difference in the worms is the major dividing feature for the eventual populous of the various phyla. there is more difference between modern humans and the first chordate than there is between that chordate and the other phyla at the time. that is, afterall, what a nested hierarchy is. the defining features at the basic level snowball as you go down the tree.just for fun, here's a phylum with no known (or rather, no confirmed) cambrian relative. or for that matter, aquatic member: onychophora, the "velvet worms." it's suspected they're somewhere between annelids and arthropods. the oldest fossils are from the carboniferous period. though it's possible that the mysterious cambrian fossil hallucigenia is related.Edited by arachnophilia, : No reason given.Edited by arachnophilia, : No reason given.

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All the more reason to think new "worms" would keep evolving/appearing, but that's not what happened. The phyla appear and no new phyla for 500 million years.Do you think we just exhausted the "worm"/phyla design options 500 million years ago or what?

Whatever was my comment at your misunderstanding in your assessment of what I wrote.You should show some humility and admit that on a very basic fact, the appearance of the animal phyla, you were dead wrong and moreover, quite insulting...."you were told" is how I think you put it. The simple fact is there hasn't been any new animal phyla in roughly 500 million years except for the one possibility that dates at least as far back as 470 million years, assuming evo dating. Is this on-topic? You mean like the battle I had with you over a basic fact, the appearance of the phyla.

Yep, or something else period. Convergent evolution shows you are wrong because similar traits according to evos do evolve independently so there is repitition in traits appearing.Moreover, I would expect a process creating the animal phyla, yes, to create new phyla, not just repeat the old ones.

I would have thought the regulars here would already know this, btw. Life During the Cambrian PeriodEdited by randman, : No reason given.

Not a new complaint from you, it seems redundant for you to repeat it so often. Perhaps you are right. Perhaps you are not. Let me answer every question in your post. It might be that you simply do not understand the counter-argument. It might be that I do not understand your argument. Instead of complaining about it, let's debate about it and try and find out what is what! If you genuinely think that your questions are not being answered and the procedure is futile then simply stop responding to posters that you don't feel are moving discussion forward. Because the ancestral population from which the phyla evolved no longer exists. It has split into a variety of lineages most of which are extinct and the rest of which has evolved. Evolved means that it has changed. If something has changed it is different. If something is different that means it isn't the same. Thus: the descendant populations are not the same as the ancestral populations. Thus: there is no reason to think that the descendant populations would have descendant lineages in the same way at the ancestor populations did. We would not expect sons to have their own uncles as offspring. If we are going to be specific, then a population evolved into the population that we later called the common ancestors of animalia or metazoa. Correct. It did evolve more - look at all the animals today and compare with the proposed early ancestors of metazoa. However, the population that evolved into what we see today no longer exists as the same thing it did then: Most of it went extinct. The rest of it evolved - rather dramatically. Today it is very very different. Thus: there is no reason to expect its offspring to be in the same area of 'design-space' as the ancestral population's offspring. There is no reason to think that the selection pressures acting on the ancestral population are the same selection pressures acting on animals today. Indeed, it should be extraordinarily obvious that contemporary animals have many different pressures to contend with. There is no rule which says that they wouldn't. They just didn't. I could ask why wouldn't Hitler's assassins successfully kill him? They hypothetically could have, but they didn't. There is no necessity for every possibility to be tried out, and most experiments that were tried out never made it this far.I have said this at least twice already, and it's an important point: if a nematode was to develop a notochord it would still be in the nematode phylum. It might be theoretically possible for something like this to happen. Maybe at this time, it is simply too improbable for the current nematode genome to change in such a way as to result in the evolution of something notochord like. The genes that the metazoan ancestor had that developed into the notochord in one lineage might have been used for some other purpose in nematodes for example and has now changed so much that the probability that it would be co-opted for notochord use is vanishingly small. Maybe it isn't improbable, has been tried out, but is not positively selected for. Maybe it isn't improbable, is positively selected for but dumb luck has ended up with any populations with notochords as going extinct without leaving any evidence (that we have so far found).Evolution does not predict that descendant populations will have offshoot branches that will likely evolve along similar lines as their ancestral populations once did. What we'd expect to see is that populations that have changed over time, will be different and will in turn have different offspring. We'd expect that different selection pressures existed in distance ancestral species and that ancestral species have a different gene pool as the descendant species and will thus be likely to evolve in different ways.

randman, Vertebrates aren't the phylum, though. Already answered this in post 41, this means you have to stop complaining this question hasn't been answered, OK? We do, they're called birds. Of course, they can never not be dinosauria or phylum chordata because they are ancestors to them. It doesn't matter if dinosaurs evolved exoskeletons & jointed legs, they would still be chordates & not arthropods. Everyone has made exactly the same point. What is so hard? It's time you understood cladistic classification & the meaning of monophyleticism. It can't be that simple, you aren't getting it. Maybe that's why you think it's magic?Massive evolutionary changes have occurred within phyla since they appeared. In any other scenario these organisms would be afforded the rank of a new phylum but aren't because of the principle of clades & the requirement for them to be monophyletic.MarkEdited by mark24, : No reason given.Edited by mark24, : No reason given.

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There are 10 kinds of people in this world; those that understand binary, & those that don't