Branchial arches or biomechanical flexion folds?

Perhaps you should do what Bernd suggests and actually explain in detail what this concept means to you, since your previously explanation was obivously framed with 'poor terminology'.Care to actually support any of this with data? I was looking at the pharyngeal pouches on some mice just today, and they don't look consistent with the degree of tissue deformation one would expect merely from the angle of curvature between the head and trunk.I will link a really seminal paper for you, one of the 500 most cited papers of all time. This is the paper describing the 'Normal Stages' of chick development by Viktor Hamburger and Howard Hamilton, it is the seminal work for chick developmental biology. A reprinted version is available as a PDF here .This goes into exacting detail over the angle of the head relative to the neck and trunk and the development of the pharyngeal arches, called visceral arches in this paper, over the entire time course of chick development. I would specifically direct your attention to plate 8, on page 35 of the PDF, which deals specifically with the development of the visceral arches.Can you use this essentially raw data to show how it is 'biomechanical flexion' that results in the visceral arches rather than any other tissue specific developmental program which may influence something such as cell growth rates, for instance, leading to the outgrowth of these structures. We will overlook for the moment that these structures share very specific anatomical features which do not appear in other nearby regions not subject to this 'biomechanical flexion' we can perhaps deal with when we understand the basis of your ideas a bit more precisely. You can try and make a case for it if you like, but you may be hard pressed. Do they give rise to structures similar to those which develop from the pharyngeal arches? Do they express genes in patterns characteristic of the 'gill pouches' such as Gcm2, Tbx1, rostrally and caudally positioned Fgf8 or BMP7 (or their respective homologues such as Dpp and Branchless)? If not then you may be mistaking a mere surface resemblance of morphology for actual homology of the features in question.TTFN,WK

AS no doubt it is typical of 'creos' to dismiss whole bodies of substantial evidence with an airy wave of the hand and a swift shifting of the goalposts. If you were merely avoiding making conclusions no one would object, instead you are concluding that evolutionary biologists are effectively lying about similarities in the developmental programs of various organisms and their relationships as determined through purely morphological studies or molecular/genetic studies.You always seem to want more details, no matter how many there are, and not even be prepared to tentatively accept the hypothesis which virtually all of the current evidence supports in the meantime. Thats strange, because laymen accept things as being true with barely any data at all most of the time. On an entirely unrelated matter I would really appreciate you finally addressing the actual account from the Sabom book in relation to van Lommel's claims on the NDE thread.TTFN,WK

Hello Randman,Now I’m starting to get a bit concerned. Up to now you seem to base your whole interpretation of Blechschmidt on the following quote from Brian Freeman[1]which is not an exact rendering of Blechschmidts description on page 42 and clearly insufficient - in the sense of lacking sufficient detail - to cover “extensive studies of early human embryos“.But we should have all at hand to correct this situation. You told me that you don’t have Blechschmidts whole book - as it seems page 43 is missing and you are therefore unable to comment on diagram 38 and 40. Let’s skip this part for the moment and concentrate on the rest of the book, specifically on chapter one and three, where Blechschmidt discusses his methodological principles and his basic concepts.First a general question: do you share the views Blechschmidt expressed in his first chapter about the relation between development and design, development and evolution, development and induction or do you consider them as outdated as his views on the influence of genetical information on development? Next, would you please describe in your words the concept of a “Densation field” (p. 37) which we will need when it comes to discuss the development of the internal structure of the pharyngeal arches. (The structure is pictured in the above mentioned diagram 40)-BerndP.S.
I have translated Blechschmidts term “Zweckmssigkeit” with “design“. A literal translation would be “usefulness for purpose” which I think doesn’t capture the intended meaning.

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References[1]Haeckel ABT.pdf

I would once again recommend to Randman that he sign up with Google to access the Google Book Search.A translated edition of 'The Ontogenetic Basis of Human Anatomy' is available through Google books. For copyright reasons you can't read through the whole book, but searching for specific key words or phrase should allow you to read a significant amount of the relevant passages.TTFN,WK

No, but it certainly removes any argument that the folds are not therefore homologous structures. If the same folds occur in essentially the same place due to the same processes controlled by the same genes then what do you have apart from an excellent example of a homologous structure?TTFN,WK

I don't have his book. The quote makes a fairly obvious point; that these are biomechanical folds, and indeed one can view embryos and see that.You guys claim homology based on molecular data, incomplete data, but still data. So make that claim.The error imo is trying to resurrect the outward appearance of the folds as evidence based on the molecular data. Let me put it this way. Let's suppose no folds exist at all. Would you not still claim homology all the same based on the molecular data?The folds due to "the embryo's head growing around the heart to which the neural tube is anchored biophysically via tension-bearing blood vessels" seems fairly straightforward as a proposition. There is an appearance of folds due to the growth pattern.One reason I mentioned caterpillars as an aside is because we see folds there as well due to the way the caterpillar grows, to illustrate a point.

Not really. Another argument is that evos are making molecular claims on insufficient data in order to resurrect the ole human gill slits myth.But either way, the folds are still biomechanical folds. That's what they are.

That's because my experience with evo claims is they are usually based on overstatements, hoaxes, and unobserved dogma. Asking for sufficient data should not be considered something loathsome, but merely following some semblance of evidentiary logic.

That isn't much of an argument though. What molecular data we have supports the hypothesis which was developed before molecular data became available, which is pretty surprising if the structres are unrelated as you claim. But as you are now putting them forward this is a meaningless distinction. Its like saying that the structures are composed of cells and thats all they are, cells.Both Bernd and I have put forward som pretty specific posts addressing your understanding of 'biomechanical folds' and their origins, perhaps you could devote some time to addressing those posts.TTFN,WK

Bleating that we don't know enough to say anything, in the face of all the evidence that we do have, is also pretty poor.Your attitude might be more convincing if you actually addressed any of the data rather than simply demanding more once some data is presented to you.TTFN,WKThis message has been edited by Wounded King, 16-Dec-2005 07:53 PM

Except that hypothesis was a hoax, based on faulty and manufactured evidence. The Biogenetic Law was wrong, but evos bought it hook, line, and sinker and have allowed it to color their perception of data. Even the lesser claim of a single phylotypic stage is wrong, and the claims of pharyngeal pouches has always been grossly exagerrated.So I think a more prudent approach is, considering the history of evo claims in this area, is to take any new claims of homology with a grain of salt, and demand sufficient evidence so we are not led down the prior paths of believing and teaching a lie, as we did for 125 years. From what I can tell, your arguments consist of claiming that because the folds are produced by a process controlled by genes, that the biomechanical folds description is inaccurate. If that is not your argument, please clarify.I concede that genes control the process, but don't see it as germane since the process controls the folds appearing.

I did address the data. The questions I raised are necessary to know if the data indicates what you claim it does. Just because some genes are expressed regulating salt intake for the parathyroid and gills is insufficient to resurrect the myth of recapitulation and insist these folds are not what they actually are, biomechanical flexion folds, and moreover, molecular data does not change that, even if it did indicate homology.

Randman, could I challenge you to a debate?I would like to show you that many of your creationist beliefs are based on "overstatements, hoaxes, and unobserved dogma". What do you think? Let me know and I will open a thread.

Yaro, we could that sometime except you are probably unaware of what my beliefs are, I suspect, based on your posts, and the next debate is with nuggins.Basically, "my creationist beliefs" primarily center around what data says in respect to evo claims. I do not hold to any one model of creationism or Intelligent Design.There are a few ideas I believe and hold to, some in respect to quantum mechanics, the fact of a deeper reality within the universe, that causal affects may work beyond a linear time-line framework, etc,...Most of my beliefs in respect to evolution come from examining the claims of evos and finding them lacking in substance.

Then....If you have nothing to replace the ToE, what's the point of deriding it?Scientists are simply going by what they see. If you don't agree with it, you have to have more than simply "I don't like these conclusions."I mean, that's fine, you don't have to like the conclusions, or even agree with them. But do you have anything better to propose?ABE: IOW, how do YOU explain/interpret the data at hand?This message has been edited by Yaro, 12-16-2005 03:34 PM