Quite apart from any factual errors, about which I’m not at all qualified to judge, here is what seems to me to be Meyer’s fundamental logical error IMO:
According to Darwin’s theory, the differences in form, or “morphological distance,” between evolving organisms should increase gradually over time as small-scale variations accumulate by natural selection to produce increasingly complex forms and structures (including, eventually, new body plans). In other words, one would expect small-scale differences or diversity among species to precede large-scale morphological disparity among phyla.
(Darwin’s Doubt, Chapter 2)
He illustrates this by asking us to comparing this figure, which he says is what we do see:
With this (appallingly badly drawn) one:
Which he claims Darwin’s theory says we ought to see.
And he says:
The actual pattern in the fossil record, however, contradicts this expectation (compare Fig. 2.12 to Fig 2.11b). Instead of more species eventually leading to more genera, leading to more families, orders, classes and phyla, the fossil record shows representatives of separate phyla appearing first followed by lower-level diversification on those basic themes.
Well, of course it does, Dr Meyer! You have just, in Chapter 2 of your fat book made an absolutely fundamental error of understanding of the entire principle of phylogenetics and taxonomy. No, of course you wouldn’t expect phyla to follow “lower-level diversification on those basic themes”. How could it possibly? And how could you possibly so fundamentally misunderstand the entire point of Darwin’s tree and its relationship to the nested hierarchies observe by Linnaeus?
All branching events, in Darwin’s proposal, whether the resulting lineages end up as different phyla or merely different species, start in the same way, with two populations where there once was one, and a short morphological distance between them. It is perfectly true that the longer both lineages persist for, the greater the morphological distance will become. But that isn’t because they started different, or because the phyla come later. It’s because what we call phyla are groups of organisms with an early common ancestor, whose later descendents have evolved to form a group that has a large morphological distance from contemporary populations who descended from a different early common ancestor.
So when a phylum, or a class, or even a kingdom first diverges from a single population into two lineages, the “morphological distance” from the other lineage will be very short. We only call it a “phylum” because eventually, owning to separate evolution, that distance becomes very large.
I’ve amended the drawings in the book as below, and, instead of labeling the trees by what a contemporary phylogeneticists might have called them, I’ve called each tree a phylum, and I’ve drawn round the organisms that constitute various subdivisions of phyla in colours from orange to green to represent successive branchings. Rather than the little bunch of twigs marked “families” by Meyer, I’ve indicated the entire clade for each subdivision, or tried to.
In Meyer’s version, he called the early sprout “ONE SPECIES”, which a contemporary phylogeneticist (Dr Stephen Chordata perhaps) would have called a “species”. But by the time of the next tree (which I think is supposed to incorporate the first), and Dr Chordata’s distant descendent comes along, she may call it an entire “genus”, and become rather more interested in the “species” that she observes it contains. Move along one to the next tree on Meyer’s time-line and an even more distantly descendent will call the whole tree a “family” containing “genera” and “species”. What was a “genus” to her great^10 grandmother will be several genera to her, and so on. And with each multi-generation of palaeontologist, the descendents of what were close relations in her ancestral palaentologist’s day are now separated by a wide “morphological distance.
So of course, if we look at the fossil record as these speciation-events were happening and try to categorise the organisms in terms of their modern descendents, we will find a great number of different phyla, and far fewer species. Of course they have different body plans, because they lived at a time when many different lineages from the first populations of rather amorphous multi-cell colonies were still around, some with not much symmetry, some with bilateral symmetry, some with five-fold symmetry, and many that didn’t go very far and left no extant lineages. Because of course Meyer also forgets the big extinction events, which are the other part of the answer to why one particular branch “exploded” while the others were never seen again. It’s even in his terrible Figure 1.11. Which he may not have been responsible for drawing, but he should at least have looked at.
ETA: the other drawing, fixed:
ETA2:
Another extraordinary example of Meyer’s complete failure to understand what a clade is, or that the words “phyla” and “class” refer to clades. Coloured emendations are mine (orange/red for Meyer’s “phyla”, blue for Meyer’s “class”):
I’d have expected an urbane, Cambridge-educated guy like Meyer to know the [ETA: spot the erroneous] singular of “phyla” but that’s minor compared to his crashing howler of an attempt to demonstrate what the term means.
ETA:3 Note: As Mung has pointed out, Meyer shows that he does know the singular of “phyla”, he just doesn’t get it correct it in this particular diagram. However, as I have said elsewhere (and above), this error is minor compared with the howler of including only a group of of descendents in his circled “phyla”, not the whole branch, which as I’ve said, undermines his entire argument.
Here is another quotation from Meyer:
Meyer has this wrong in a very important way. Palaeontologists call the number of higher-order taxa in an environment (i.e. at a particular time) “disparity”, and far from being different from “diversity”, it’s one of a number of measure of diversity. An environment can be diverse even if it consists of just one taxon, with lots of sub taxa; it could also be diverse if it consists of many taxa, each represented by only one branch.
And so his claim that we should expect diversity to follow disparity doesn’t even make sense. We certainly would expect taxa to diversify, and we see that we do. But we wouldn’t expect to see the total number of higher- level taxa increase – in fact, by definition, they can only reduce. If originally there were, say, six basic body plans (forms of symmetry, say), and only two left lineages further down, then clearly the number of taxa present when there were six of them is smaller than later on where there are only two. In the mean time, those two have diversified.
But there’s nothing problematic about that for Common Descent. Nothing in the hypothesis of Common Descent requires that all bifurcations leave lineages that don’t go extinct, and they clearly don’t.
Are you reading what you post:
Meyer:
Darwin’s theory implied that as new animal forms first began to emerge from a common ancestor, they would at first be quite similar to each other, and that large differences in the forms of life – what palaeontologists call disparity – would only emerge much later as the result of the accumulation of many incremental changes.
Lizzie reading Meyer
And so his claim that we should expect diversity to follow disparity doesn’t even make sense.
Let’s start with something much simpler that contains the same concept.
When two hydrogen atoms and an oxygen atom form a water molecule, how much like hydrogen or oxygen is the water molecule?
First my comment is about Lizzie is saying Meyer says the opposite of Meyer is saying in the quote reported by Lizzie.
No scientific problem but coherence problem.
Second adding H2 and O2 is an exaple of evolution?
Yes, but I don’t think you are reading what I post!
If disparity is a measure of diversity, how can disparity either precede of follow diversity?
Diversity increases over time, in general, although big extinctions events will reduce it (as do local extinction events now).
That’s is not counter to what we’d expect under common descent.
However, what are the largest-grain taxa in at one time will tend to be fewer much later, because they can only get less numerous, not more.
That’s because all large-grain taxa start small.
That’s the explanation for Meyer’s “puzzle”. i.e. it isn’t one.
Is this true? He is claiming that diversity follow disparity?
Where?
Small differences accumulate into large differences, yes. Who’s arguing the other way? Meyer!
You are using ‘disparity’ as some kind of metric applicable to the whole limb – essentially, a synomym for the taxon. If it’s disparate at this end, it’s disparate at the other end too. Which is rubbish. Certainly if one takes account of the genetic evidence, which points strongly to initially closer relatedness followed by cumulative divergence, just as at every other taxonomic level. Not just here in the Cambrian, but at any other radiation you may care to point to, where the fossils appear rather suddenly. Of course, the roots of the tree are not richly represented in the lower Cambrian. So what? This would have been more a problem for Darwin than the modern miner of gene level information, but there are plenty of reasons other than nonexistence for the paucity of precursors. You think there is no allowance to be made for sampling bias in fossilisability and discovery?
So you are going to tell me there were witnesses to Creation? Plus, you are wrong. Languages contain degrees of similarity and dissimilarity which can be used to join the dots where historic evidence is absent. Likewise genomes. You may have only had sex with the lady once, but the child’s genetic makeup is clear evidence of the act. More distant relationships – interspecies, interfamily etc – are equally amenable to investigation. No doubt you draw some invisible boundary beyond which genetic evidence is inadmissible. If you draw it round each species, you are a clown and not worth talking to. If you draw it a little wider, on what basis do you determine that?
I didn’t discard anything. I asked you whether you thought that God (rather than a chain of communication) accounts for the similarities and differences in language.
Each poor fit decreases the confidence level. It does not send it immediately to zero, nor is the data just thrown away. What remains is generally still sufficiently high in the confidence range to support the hypothesis that there is an underlying tree. That’s the little number you often see on a branch. You think phylogenetic methods are only valid if every last data point converges on the same tree? Despite known sources of departure – homoplasy, LGT, indels etc? No, I suspect what you really think is that systematists don’t know the first thing about their own subject.
Huh? A non sequitur.
Well, that was a joke, hence the smiley. Nonetheless, I jumped in initially because you were talking nonsense about the expectations of a diverging, branching process, confusing different species concepts, and regarding the difficulties of labelling particular sections of the tree as difficulties for its actual formation. We were talking of monophyly, and suddenly you came back with the irrelevant “well if monophyly is true Lizzie is still wrong”! Now you offer “If she is wrong, you are wrong.”. Indeed. But you haven’t been at all clear about what.
Oh, grow up!
As you said “not worth talking to”.
A perfect real-world example of diversity/disparity can be found among the Middle East Blind Mole Rat (Spalax ehrenbergi). There are four species created by chromosomal mutation (Spalax galili, 2n = 52; Spalax golani, 2n = 54; Spalax carmeli, 2n = 58; Spalax judaei, 2n = 60), and four more created by ecological pressure/selection (Spalax ehrenbergi, 2n =60) in the superspecies located in Jordan. In all these events are thought to be examples of either allopatric or peripatric speciation. Now there is evidence (mtDNA, physiology, and behavior) that sympatric speciation is occuring within Spalax galili, 2n = 52. Despite the various ways several new species have formed from a very recent common ancestor, their morphology is deceptively similar to even the trained eye.
http://www.pnas.org/content/110/7/2587.full
Then why are you having trouble with divergence and the emergence of different body plans?
Take a look at some other systems that are constructed of only carbon atoms. The are called the allotropes of carbon.
This is just carbon atoms. You can easily go on line and find other simple arrangements of atoms that become the templates for further development.
At the very simple level of one celled creatures, made up of simple structures of molecules, you will find small changes in the structures of these molecules lead to completely different templates on which to build a creature.
So at the earliest stages of evolution is where we will see the emergence of the templates on which life on this planet is based.
Not all the templates that are possible may have survived, but at the earliest stages is where we will see the emergence of body plans. That diversification can take place very quickly at these simple levels. Once established, they branch into different lines of development.
Simple systems of molecules, even molecules made up of one type of atom, can form a number of different templates.
Children learn these kinds of things. Just Google ”magnetic marbles” to find all sorts of things one can do with a few simple templates.
Sorry, Blas, if I expressed myself over-robustly.
Blas:
Here, though not quite explicitly: “In other words, one would expect small-scale differences or diversity among species to precede large-scale morphological disparity among phyla. […] The actual pattern in the fossil record, however, contradicts this expectation”.
The contradiction may be that they are simultaneous, rather than reversed, course.
This is the saltstion argument.
I already have. You are apparently immune to the point.
It’s not my job to attempt to disabuse you of your conceptual blindness.
I don’t think its realistic to pin a supposed theoretical “fact” on something so lame as “the dog ate my homework” just-so stories. Genetic commonality speaks to common descent. … and so I have to disabuse you of that straw man one more time, immune as you and other Darwinists are to the distinction between the modules of your own theory.
You have no evidence that supports the Darwinistic evolution (RM & NS) of body-plans in the Cambrian. The known evidence contradicts the Darwinist story-telling. Your ilk just cannot admit it. That you keep substituting evidence for Common Descent as if it spoke to the problem demonstrates your position incapable of addressing the actual issue.
WJM to English Translation:
“It’s not my job to back up the blustering scientific ignorance I belch forth here on a regular basis. ”
What is your job here WJM, besides the obvious one of comic relief?
Well, except for all the genetic evidence and the data from Precambrian strata we do have. You know, all the data that Meyer ignored.
LOL! No it doesn’t, not even a little. Having incomplete evidence doesn’t make the evidence we do have somehow contradictory.
What issue would that be? That Meyer wrote a Creationist propaganda book for political purposes in which he dishonestly ignored and/or butchered the actual scientific evidence for life’s development in the Cambrian? Seems to me real science is addressing the issue quite well.
William,
Your self-imposed, stubborn ignorance of the science is your shield against any evidence that anyone could hope to present. If you don’t look, you don’t have to see what you don’t want to see.
Last chance; take a look at a recent book, Life’s Ratchet.
While you are waiting for the book, take a look at this video by the author.
Lizzie,
Willam Murray responds:
.
So WJM declines to clarify “diversity” and “disparity” as he understands the terms (in a way that brings to mind the parable of the mote and beam).
Lizzie adds helpfully:
May I ask for clarification of “diversity” and “disparity”? Do they have more than qualitative meaning in evolutionary biology? I mean I see talking about diversity (perhaps biodiversity would be clearer, more specific?) of an ecosystem, the number of different species present in a particular environment, is quite straightforward.
Disparity seems much less current as a concept. In general usage, it means dissimilarity, so describing two species as disparate might indicate they are not closely related. I get very few hits for biodisparity but it threw up an article that seems to have sparked a lively discussion on terms such as biodiversity, biodisparity and bioequivalence and how clear and consistent definitions are needed. I begin to understand why WJM might be struggling.
Now, I clearly see what Lizzie is getting at if she states Meyer’s point correctly. We find surprising diversity in the Cambrian fauna but do close studies demonstrate disparity? I don’t think so. Plenty of segmented bilaterally symmetrical armoured animals. Where’s the disparity? Ancestors of subsequently disparate phyla may have been (and would have to be, for evolution to be true) close cousins. I don’t see any contradiction to that in the fossil evidence from the Cambrian period.
What is your evidence that they were designed by an intelligence? Oh, that’s right, you are not making that argument!
Lucky that really, as I happen to know you have no evidence for that. I guess it’s just a coincidence that you are not making an argument for which you already know there is no evidence.
Pathetic really.
William J. Murray,
A strawman? What’s being misrepresented? Yes, genetic commonality speaks to common descent. It offers no support to the theory that a designer constructed the phyla, but does offer support to the theory that descent with modification led to the diversity/disparity that appears. Even if those earlier organisms have not been preserved in available strata. There are indeed many potential reasons for that non-appearance, and only a committed Deny-at-all-Costs merchant would dismiss all but “they never existed”.
Not least is the extreme rarity of soft part preservation. Burrows almost identical to those of priapulid worms appear about 540 mya. But not one of the animals that made them. Fully 5 million years later we get the first molluscs – shells. But not the animals inside. Only very unusual preservation conditions such as at Sirius Passet and Chengjiang (c517 mya) and the Burgess Shale (c505mya) have preserved soft parts. Those localities in total would provide a few hundred yards of roadstone, and of course much has been eroded or subducted. So it is entirely rational to consider that there is much that is cryptic – 35 million years from burrows to Burgess is a lot of evolutionary time, and it’s a big old world. Only freak snapshots have shown anything besides those shells and exoskeletons. The amusing part is that Meyer’s thesis largely depends upon the rarity of these localities. Phyla appeared here, here and here. Nothing led up to them – if it did, how come we don’t have a whole bunch of other ‘here’s to prove it? Well, darwinist? Dog ate your homework again?
Here’s an exercise – draw the ID timeline and insert at appropriate points those transformations which the Designer was responsible for, with reasoning.
Evidence for a tree (common descent) contradicts the theory that the phyla originate from gradual modification? Hardly. (Someone must have pointed out by now that “RM+NS” is not a complete description, even as shorthand, of the evolutionary process? You seem to get your science from the Comments section of Uncommon Descent.)
Heh heh. The fact that you don’t see the relevance of common descent evidence, and seem to insist that the fossil record should preserve everything of interest “if Darwinism were true” demonstrates your own ilkiness rather nicely.
Yes, I admit to having read ‘disparity’ in an informal way, when it tends to mean a significant difference between two things – such as, to apply it to biology, between two representatives of different phyla. But it seems to be used in palaeontology to represent the number of distinct groupings represented in a collection. Diversity would be the number of countably different species, disparity the number of higher taxa represented. You could have high diversity but no disparity, or disparity could equal diversity, but it does not seem that disparity could exceed diversity.
And indeed we do get such disparity in, say, the Burgess fauna. Gould made similar points in Wonderful Life. He argues that phyla appeared early, not that they had no precursors, and that there were once more than there are now.
What it really appears to mean is that there are members of these biota that are recognisably in the same clade as modern arthropods, or molluscs, or chordates, etc, on phenetic grounds, and other stuff we can’t assign. This method guarantees that they will appear ‘suddenly’! Even if you had the succession preserved, there would be a discontinuity between things that you could not put in the clade (on phenetic grounds) because they were insufficiently like the modern type, and those that you could – even if you had in your hand genuine ancestors or transitionals.
Ilk spotted!
William, can you succinctly summarise the case you think Meyer is making?
Because the case I think he is making is this:
Common Descent predicts that disparity (as measured by the number of phyla) should increase over time, with ever more body plans emerging. In fact we see disparity (as measured by the number of phyla) remaining static, or reducing.
Therefore Common Descent does not fit the evidence.
And the flaw in it, as I see it, is that Common Descent does NOT predict that “disparity”, as measured by how many taxa at a particular taxonomic rank (e.g. phyla) there are, should increase over time. It doesn’t even predict that diversity will always increase over time – it will predicts that diversity will tend to increase between major environmental upheavals, during which it may dramatically reduce, in what are called “extinction events”.
And as time goes on, the number of the taxa at the highest economic ranks will tend to reduce, while the number of taxa at the lowest economic ranks will tend to increase.
Thanks, Allan.
Had to Google phenetics. I am aware of the tension between taxonomy and cladistics but it seems that phenetics is largely superseded by cladistics these days.
I’ve already done so. I’m finished with repeating things for you that you are either unwilling or unable to understand.
No, Meyer doesn’t argue that disparity should, under current ToE, increase over time, because there’s no way to predict how much “disparity” evolution will produce at all – it didn’t have to produce any disparity whatsoever, under current evolutionary theory. Which is another failure of current evolutionary theory; the main components, RM & NS, don’t actually predict anything. They’re just used to satisfy ideology.
I see the relevance of the evidence for common descent for both the design and non-design arguments. If the evidence showed what Darwin pinned the success of his theory on – gradualism up to major body plans – then the evidence would be weighted towards Darwinism (at least until you attempt to solve the RM & NS limitation problem).
However, that is not what we actually find. What we actually find is common descent showing a pathway where there has been variations on structural themes, not descent into novel structures from prior ancestors.
That diversification does not apparently lead to disparity (from fossil and observable evidence, given generational studies of bacteria) renders common descent more of an argument for a design feature that allows diversity to play out up to a certain point, but not into disparity, which apparently requires design to pull off.
We empirically observe that wind and water can produce erosion. But since wind and water theory doesn’t actually predict the shape of the Grand Canyon, that means the main components of Geology, “wind and water” are invalid. They’re just used to satisfy ideology.
Is that what passes for logic in WJM-world?
I’ve already done so several times. It’s blatantly obvious from the context I use the terms in every time I use them. Ron White.
WJM, I’d really like to see you take Allan Miller’s challenge. Draw the ID timeline and insert at appropriate points those transformations which the Designer was responsible for, with reasoning. Explain how Meyer’s Cambrian claims fit in with our 3 1/2 billion year record of life on the planet.
You up to the task? Let me guess – it’s not your job. 🙄 Your job is just to blindly attack without understanding anything to do with the actual evolutionary sciences, right?
You seem to get virtually all of your understanding of evolution from comedians instead of scientists. That’s the whole ID movement in a nutshell actually.
I’m calling your bluff, William. Last time you said you’d done something earlier, I did an exhaustive search, and I found nothing. I’m still waiting to hear how you are distinguishing “disparity” and “diversity”.
Meyer’s argument hangs on those two concepts, so until you have clarified what you mean by them, or what you think Meyer means by them, you haven’t summarised his argument.
Meyer:
You may disagree with Meyer that large-scale morphological disparity, should, “according to Darwin’s theory” “increase over time”, but I’m not in this thread addressing your critique of Darwin’s theory, but Meyer’s.
Meyer is saying this, and he is correct that morphological diversity will, in general, tend to increase over time; where he is wrong is to expect the number of phyla (or other large-grain taxonomic categories) to increase over time, under either Common Descent, or Darwinian evolution (not the same thing, btw).
You are correct that Darwinian evolution does not necessarily predict diversity, and nor does Common Descent. A lineage can peter out, and Darwinian adaptive processes can maintain a population at an optimum, as well as adapt it over time. Furthermore, Darwin did not, oddly, tackle speciation as we now use the term.
But branching lineages where the tips of the branches are increasingly diverse is completely compatible with Common Descent, and, indeed, Common Descent is reasonable inference from such a pattern, as long as we also have a theory that could account for the diversity given branching, and Darwin’s theory does so – the theory of adaptation, by means of heritable variance in reproductive success, to which we can now add drift, which also accounts for speciation (i.e. the branching).
It’s blatantly obvious to me from the context that you have neither understood Meyer’s use of the terms nor mine.
Meyer’s argument is that if we find disparate body-plans (which we do, and call phyla) then according to Darwinism, we should find, preceding that disparity (different fundamental body-plans that appeared in the Cambrian), diversity from a prior body-plan (pre-Cambrian) leading up to the new body-plan.
It’s not that we should find disparate body plans in the first place (no way to predict that from evolutionary theory), but that given that we have found them, and have found them virtually all to originate in a small slice of evolutionary time in the Cambrian, then we should find gradualistic evolutionary precursors leading away from prior forms towards the new forms in the pre-Cambrian.
Also, if all it took was 30-70 million years to generate all the major body plans we now find, why haven’t any new body plans been generated in the 500 million years since?
Nice try Lizzie, you started in the post with a species phyla problem:
“So of course, if we look at the fossil record as these speciation-events were happening and try to categorise the organisms in terms of their modern descendents, we will find a great number of different phyla, and far fewer species. Of course they have different body plans, because they lived at a time when many different lineages from the first populations of rather amorphous multi-cell colonies were still around, some with not much symmetry, some with bilateral symmetry, some with five-fold symmetry, and many that didn’t go very far and left no extant lineages”
And then you move to say that Meyer said what he wasn´t saying about what come first if diversity or disparity:
“And so his claim that we should expect diversity to follow disparity doesn’t even make sense. We certainly would expect taxa to diversify, and we see that we do. But we wouldn’t expect to see the total number of higher- level taxa increase – in fact, by definition, they can only reduce. If originally there were, say, six basic body plans (forms of symmetry, say), and only two left lineages further down, then clearly the number of taxa present when there were six of them is smaller than later on where there are only two. In the mean time, those two have diversified.”
Now you changed again
And I will admit that this maybe is an error from Meyer if he is saying that darwinism require increasing disparity, but really I don´t see clearly in th quote you posted that that is Meyer´s claim.
What I still see is that you are not aknowledging the problem for darwinism with CE:
Lizzie:
But branching lineages where the tips of the branches are increasingly diverse is completely compatible with Common Descent, and, indeed, Common Descent is reasonable inference from such a pattern, as long as we also have a theory that could account for the diversity given branching, and Darwin’s theory does so – the theory of adaptation, by means of heritable variance in reproductive success, to which we can now add drift, which also accounts for speciation (i.e. the branching).
The problem with CE is that you have tip of an “immaginary” branch.
Is better to admit that your originl post is a mistake and then we can move on and discusse about immaginary branches or if we have o espect diversity and disparity or only diversity.
Well, no, it isn’t. But I’ll accept it as yours.
So here’s the problem: firstly Darwinism merely predicts that such a prior body plan (one ancestral to the later phyla) existed – whether we find it or not may depend on whether it was preserved. Secondly, luckily, such prior body plans are actually found, in some cases within the Cambrian (because, contrary to your persistent habit of treating the “Cambrian” as a single event, it was a long period of radiation, within which we see ancestral taxa divide into sub-taxa. These sub-taxa include phyla. I’ve already mentioned deuterostomes, which are ancestral to two separate body plans – chordata, which include us, and echinoderms, which include starfish. I assume you agree that starfish body plans and ours are radically different.
Thirdly, we also find fossils with body plans ancestral to disparate Cambrian body plans in pre-Cambrian strata, although these are necessarily rarer, because fossilisation is necessarily rarer, and preservation of fossiliferous rocks necessarily scantier, the further back you go.
But absence of evidence is not evidence of absence, especially when we do in fact have some fossil, when there are clear reasons for the absence of evidence, and when the postulate is independently supported by molecular data.
Not only do many of them originate later in the Cambrian, many of the evolutionary precursors are observed in the earlier Cambrian as well. The Cambrian itself is rich with evidence for branching lineages, including new body plans (new phyla; very different body layouts e.g. single spinal nerve vs five radial radial nerves).
I can’t really make sense of the last part of this, though. And I’m no longer even sure what you mean by “originate”. If you mean the point at which one lineage splits from another, then we do see lots of that in the Cambrian, but that’s because we also see the unsplit precursors.
It took vastly longer than that, William. It took 2.3 billion years for multicellular organisms to evolve in the first place. It then took a further billion years to get to the beginning of the Cambrian. During that time – from the beginning of multicellular life to the beginning of the Cambrian – a vast number of “body plans” were “generated”. We can see some of them in the Ediacaran, although fossils are necessarily scarce as they were mostly soft-bodied. But the Ediacaran is extremely diverse.
Of the Ediacaran organisms, most did not leave descendents in the Cambrian. Of those that did, many diversified further, into yet further ways of organising a body, and were extremely successful.
Why are have there been few new ways of organising bodies since then? Because those that survived were the successful ones! And they already had a body-plan.
Body plans, are genetically hierarchical. Genes that control whether an organism develops into a bilaterally symmetrical or a radially symmetrical adult, for instance, are expressed early in development. In a simple organism that doesn’t do much development, a variant that converts bilateral symmetry to radial symmetry may result in a perfectly viable organism. In an organism that is the scion of a long and noble bilateral lineage, a variant that converts bilateral symmetry to radial symmetry will almost certainly be lethal.
So you wouldn’t expect complex bilateral organisms to suddenly spawn radial offspring. And you won’t get radial offspring from a simple non-radial organism if the simple non-radial organism has been eaten out of house and home by various starfish and naked apes.
Which we do find. Just not in the unrealistic quality and quantity that Creationist philosophers like Meyer demand.
Because at the beginning of the Cambrian all those evolutionary niches were wide open. Once the initial baseline forms were established nothing has come along since to outcompete the originals which already have a huge head start.
Once again, you could answer your own questions by reading any freshman level biology text, or with a 30 second Google search. But that assumes you don’t wish to remain willfully ignorant.
Me:
In fact, let me update that rather watery apology:
Blas, please accept my sincere apologies for any offence caused.
I have been on the receiving end often enough to know what it looks like, and there is nothing like having one’s words cast back to pull one up short. I don’t do this to cause offence, and if I have, I sincerely apologise.
Allan
Stop moving the goalposts. The “Cambrian Explosion” problem, as far as it is a problem, involves explaining how pre-Cambrian life could give rise to the collection of body plans we observe in the fossil record (assuming we are interpreting the fossil body plans correctly).
What is the proper answer to the question “why have we seen no new body plans since the Cambrian?”? Possibly because the body plans generated in the pre-Cambrian (the time that Meyer pretends doesn’t exist) are sufficient to occupy all ecological niches available at the time. In that case, natural selection will trim off every slightly-less-optimal body plan. And then all future body plans will inherit from the ones that survived.
Why are there no nine-legged arthropods? Because the developmental cost of the extra arthropod leg outweighs the benefit, so natural selection trims out any nine-legged mutants. (this is a testable hypothesis, so if you disagree with it, feel free to carry out the relevant experiment and report your results).
Why are there no cats with wings? Because there is no genetic history available to a cat to develop functional wings. Well, that isn’t exactly true, in theory you could revert the mutations that separate a cat from its most recent common ancestor with a bat and then mutate forward to the bat descendent.
But you would only bother attempting this if you subscribed to the Axe/Gauger Theory of Intelligent Design.
Ok, apologies acepted.
Yes, he is saying that. He says it many times. I’ve typed out a few of them. Here’s another, from near the end of that same chapter:
It is of course completely true that disparity increases over time. But Meyer doesn’t notice this, because he thinks that a phylum only includes the later descendents of a branch, not the whole branch. The phylum branch must begin before the others.
The branches are not “imaginary”, Blas. They are certainly postulated but they are also supported by actual fossil exemplars.
That is not what I admited may be an error. That quote is about diversity and disparity and you are returning to your first claim that phyla starts before or after genera that is a semantic discussion.
Again to the first point.
Tell me Lizzie according to darwinism titaalik is a fish or an anfibian?
Well this is more interisting. Something that is scientifically postulated and supported is real? Science are more than models that explin realities? Are the model reals or imaginary’
Yes, it is. But if Meyer is going to claim that disparity comes before diversity on the basis that when palaeontologists talk about phyla they are talking only about descendents on a branch, not the whole branch, then he needs to point out that by redefining “phylum” in that way, he also needs to redefine “disparity” to fit. Otherwise it is simply the fallacy of equivocation – define a word one way to make one point, then a different way to make a different point, and then claim that the same concept is referenced in both points.
It depends on what you mean by those terms. Tiktaalik is in the class Sarcopterygii, which is a clade that includes lobe-limbed fish. It is not in the class Amphibia. It was however “amphibious” i.e. it lived both in and out of water.
If you want to regard models as “imaginary” feel free. To some extent all our percepts are what we “imagine”, including the computer that I am “imagining” is in front of me. But if a model is well supported by data, we do not normally call it “imaginary”.
But yes, models are all we ever have in science. Many of them are extremely good, by which I mean they account extremely well for our data and predict new data. Which is probably why you are alive. It’s certainly why I am.
Looking at what you said here
Seems that what you have to apply to yourself what you say here.
I agree with this.
probably we are going to differ in what a model describe and what can predict.
I’m not understanding your point, Blas, but if you think I was equivocating over Tiktaalik, it was quite the reverse. I was making a very careful and clear distinction between different uses of the words “fish” and “amphibian” precisely so as NOT to equivocate.
But perhaps that wasn’t your point.
I’m not quite sure what you are agreeing with.
A good model should describe existing data and predict new data.
I don’t see how the Cambrian helps the case FOR (an) intelligent designer(s). Why the long wait – two and a half billion years – between the first cells and multicellular life, when the designer(s) needed only 1/5th as much time to go from a few dozen basic body plans to a planet full of complex lifeforms of every sort imaginable? The implication is that either the designer(s) were learning as they went, becoming more proficient with time; or that designing simple multicellular life is 5 times more challenging that designing human beings.
Elizabeth:
You have a model for the Cambrian?
Elizabeth Liddle:
Your insinuation that Meyer doesn’t know the singular of “phyla” is hardly justified considering what he wrote in the chapter you reference in the OP:
Maybe you’re just being uncharitable, Elizabeth, and I guess that’s ok, because ID’ists don’t deserve charity anyways, least of all here at “The Skeptical Zone,” where even obvious gaffes like yours can go unchallenged by “the Skeptical Choir.”
Meanwhile, over at UD, your name came up as a “charitable” opponent of ID. Go figure.
rhampton:
In my best Mike Elzinga impersonation, read the book.
Elizabeth Liddle:
You’re the one equivocating, Elizabeth. You’re equivocating over the terms disparity and diversity and phyla, as was pointed out to you over at UD.
You claim that disparity is a measure of diversity. That’s just wrong.