ExYECer
Posts: 36
Joined: May 2002
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Dear Nelson,
May I suggest that when you quote from Answers in Genesis that you at least provide for the correct reference? And it would be helpful that you would indicate that you are quoting from a secondary source.
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The eye of a lobster (and some other 10-legged crustaceans1 including shrimps and prawns) shows a remarkable geometry not found elsewhere in nature—it has tiny facets that are perfectly square, so it ‘looks like perfect graph paper.’2
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2. Hartline, B.K., Lobster-eye x-ray telescope envisioned, Science 207(4426):47, 4 January 1980.
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And while at smaller resolution indeed this may seem to be perfect, reality shows that at high magnification they are hardly that perfect.
Another example of these 'perfect squares' in prawn shrimps
I would like to point out that my main objection is to Nelson's claims that no evolutionary pathways or selective advantages have been shown for the evolution of eyes, particularly in lobsters and Pecten. By relying on second hand resources which have been shown to be of doubtful accuracy in many other areas, Nelson has been furthering an argument for which he does not seem to have any first hand information. And yet he is willing to make claims that would go beyond what would be supportable without any knowledge of first hand sources. This has led Nelson to make such assertions as 'perfect squares' when in fact the photos show that they are hardly such. Other mishaps have been documented elsewhere and in the rest of this posting.
The moral of the story is that if one wants to argue that t is the failure of natural selection and RM alone to account for these eyes that opens the door to front-loading. one should be familiar with the actual evidence and not some second hand resource.
Nelson still seems to be unable to grasp the simple fact that the observation that Pecten needs to see in and outside the water may explain the selective advantage of an eye that can see in both environments. The difference between the Pecten and its precursors need not be that large when one realizes the likely pathways.
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As noted in Chapter 1, the case of Pecten is fascinating. It has evolved an eye with two separate retinas placed
next to each other but separated from the tapetum and other elements at the posterior of the optical orb. The
tapetum has become a reflective mirror in a catadioptric optical system consisting of the objective group and the
tapetum. When the eye is immersed in sea water, the cornea is ineffective but the crystalline lens and the tapetum
combine to form a catadioptric optical system bringing light to focus on one of the two retinas. When the eye is
not immersed in sea water, the cornea of the objective group is effective and the cornea and crystalline lens operate
as a dioptric optical system with the other retina. This provides an animal living in an estuary with focused vision
under both aquatic and terrestrial conditions.
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From "PROCESSES IN BIOLOGICAL VISION by James T. Fulton"
First of all the reflector. It should be noticed that
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The tapetum sheet can evolve to form a variety of functions depending on the animal. It is generally a passive
layer. Normally, it can aid in the absorption of stray light that has passed through the retina. In some cases, it
consists of small groups of cells that act as a retro-reflector to direct light back through the retina. As seen in the
case of the mollusc, Pecten, the cells can also be used to form an optically coherent sheet of cells that form a
reflecting optical element in a catadioptric lens system.
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Ibid
Now the retina
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The individual photoreceptors are similar in structure to those of Arthropoda, i.e., the chromophoric material is
found in rods exuded from the sides of the photoreceptor cells. .... Whereas the rhabdom of Arthropoda
exhibits a circular symmetry with respect to the centerline of the assembly, this is much less evident or
nonexistent in Mollusca. The limited data available indicates an orthogonal grouping of photoreceptor cells
to achieve a higher sensitivity to the polarization of the incident light.
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Ibid
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It is the failure of natural selection and RM alone to account for these eyes that opens the door to front-loading.
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In fact you have failed to show that RM&NS are a failure to account for these eyes so there goes your justification for front loading but you seem to still be unable to describe to us what front loading really is, other than not RM&NS..
Describe your front loading scenario in some detail please. And explain what mechanisms you have in mind that played out for times > t_0 (the time of front loading). I would encourage you to check out some of the works on Intelligent Design that would allow you to familiarize yourself with the concepts and their strengths and weaknesses.
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3. You say: " Spondylus Until Nelson can show us from the original research papers what the eye of the Spondylus looks like as compared to Pecten we have no real way to discuss this."
You did this yourself:
Francis:
In the Spondylus and Pectinidae, the eyes are quite well developed consisting of a cornea, lens and retina.
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That suggests to me that Nelson is not familiar with the primary sources that describe the eyes of Pecten and Spondylus. In fact as far as I have been able to tell Spondylus eyes are not like Pecten eyes at all.
For instance from Ibid:
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use of two separate optical forms within the available physical envelope in Pecten, including introduction of an
entirely new optical form to animal physiology--a catadioptric lens system.
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Pecten seems to be unique in this aspect. Perhaps Nelson can present us in some more detail Spondylus? Which species of Spondylus btw is Nelson refering to?
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Anyway, my discussion of front-loading and eye development center around pax-6. Pax-6 has remained more or less the same in most branches of life. In every animal examined that has eyes this gene proves to be involed in eye development. Moreover, it is necessary for function. In both Mice and flies pax6 mutations severely affect development of eyes. Drosophila has two closely related pax6 genes, eyeless (ey) and twin of eyeless (toy). Expresssion of either of these genes in antennal, leg and wing imaginal discs in drosophila causes well formed ectopic eyes. In xenopus embryos ectopic injection of pax6 into blastomeres causes ectopic eye-like structures. So not only is Pax6 required for eye formation, it is also the author of eye development. Pax-6 genes control both upstream and terminal functions in the gene network for eye development. Since pax-6 genes also exist in primitive organisms like sponges, a prediction of FL (Mike or Warren can correct me if I'm wrong) would be that it plays a non-essential role in these organisms.
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So far so good so we have evidence that evolution shaped the expression of the Pax-6 gene as well as many other hox genes. But how does this show evidence of front loading? That essential genes have changed little over time but have been quite able to lead to different evolutionary shapes shows how a simple variation on the timing of embryological development may have a significant impact on the resulting form. But as with Mike Gene, Nelson is now painting an arrow around the bullseye by arguing that evidence of common descent is suddenly evidence of 'front loading'. Well we all agree that at t=t_0 pax-6 gene existed as an initial condition and how RM&NS played a role in shaping life there after. If Nelson wants to argue front loading then he surely has to accept the role of natural forces shaping evolution for t>t_0 or he is arguing for intervention rather than front loading. But while evolution can explain in a non ad hoc manner the evidence, Nelson seems to want to argue, without much evidence, that this front loading or initial condition required intelligent design. Yet in the actual discussion Nelson seems to be wavering between front loading and intervention and so far has been unable to provide us with the necessary details.
Nelson claims that the quote came from Denton but according to "Design in Nature by HARUN YAHYA" the reference in Denton is:
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The eye of a lobster shows a remarkable geometry not found elsewhere in nature - it has tiny facets that are perfectly square, so it "looks like perfect graph paper."2
2. J.R.P. Angel, “Lobster Eyes as X-ray Telescopes”, Astrophysical Journal, 1979, 233:364-373, cited in Michael
Denton, Nature’s Destiny, The Free Press, 1998, p. 354 |
The reason I thought it was AIG was because your reference
Land, M.F., Animal eyes with mirror optics, Scientific American 239(6):88–99 1978 matches their
Land, M.F., Animal eyes with mirror optics, Scientific American 239(6):88–99, December 1978 remarkably well.
In either case your reference seems to be erroneous as far as I can tell. This can be avoided by actually reading the references from which one quotes. In fact relying on Denton is never a good policy, which is why I included some references to reviews which show some serious shortcomings in his interpretation of scientific work. The author may have refered to them as looking like perfect squares but I have shown they are hardly such, especially when realizing the relevant optical wavelengths.
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