Hello,
"To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree." (Darwin 1872)
As you see Darwin observed the difficulties of the evolution of the eye, what we need is a document to show that the eye undergone gradual changes( by means of Darwinian mechanism) but as we see no such document exist, if it really exist then we can observed a partially formed eye. Like for example an eye with out a retina, an eye eye with out a cortex. Can you find me one?
"Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound. .
If reason really tell Darwin that the eye evolved, then he should observed the following
evolutionary stages of the eye. The following are the stages, which Darwin though necessary to support his idea.
1.photosensetive cell.
2.aggregates of pigment cells with out a nerve.
3.an optic nerve surrounded by pigment cells and covered by translucent skin.
4.pigment cells forming a small depression and then a deeper depression.
5.the skin over the depression gradually taking a lens shape.
6.evolution of the muscles that allow that alllow the lens to adjust.
Maybe you would reason out that all of these are viable because we observed it living things today. As Professor Jerry Coyne reason out;
"The increments between these steps are slight and may be broken down into even smaller increments. Natural selection should, under many circumstances, favor the increments. Since eyes do not fossilize well, we do not know that the development of the eye followed exactly that path, but we certainly cannot claim that no path exists.’5
And Dennet put the idea in a dominant way he said;
"‘ rare accident giving one lucky animal a mutation that improves its vision over that of its siblings; if this improvement helps it to have more offspring than its rivals, this gives evolution an opportunity to raise the bar and ratchet up the design of the eye by one mindless step. And since these lucky improvements accumulatethis was Darwin’s insighteyes can automatically get better and better and better, without any intelligent designer.’7
But other scientist are not comfortable of these views like for example; Melnick he concluded that eye could not undergone evolution by means of Darwinian process he said;
"its immense complexity and diversity in nature, as well as its beauty and perfection in so many different creatures of the world, defies explanation even by macroevolution’s most ardent supporters.’8 And university of Salford biologist Laurence R. Croft said;
"precise origin of the vertebrate eye is still a mystery. The fascinating thing about the evolution of the eye is its apparent sudden appearance."
In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection.
Here is the problem of this reasoning. "The monophyly of the Articulata (= Annelida + Panarthropoda), proposed by Wgele et al. (1999), is contradicted by all molecular data that support either Ecdysozoa (including Panarthropoda), or Lophotrochozoa (including Annelida), or usually both."
In certain crustaceans, for instance, there is a double cornea, the inner one divided into facets, within each of which there is a lens shaped swelling. In other crustaceans the transparent cones which are coated by pigment, and which properly act only by excluding lateral pencils of light, are convex at their upper ends and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance
If those things really exist how does division of the parts and coated by pigments show the gradual transition?
With these facts, here far too briefly and imperfectly given, which show that there is much graduated diversity in the eyes of living crustaceans, and bearing in mind how small the number of living animals is in proportion to those which have become extinct, I can see no very great difficulty (not more than in the case of many other structures) in believing that natural selection has converted the simple apparatus of an optic nerve merely coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the great Articulate class."
Again if you are correct then fossil record must support these view even Darwin acknowledge it "the crucial importance of this requirement to the theory of evolution was fully understood by Darwin, who stated that, in searching for the gradations through which an organ in any species has been perfected, we ought to look at its lineal progenitors. Indeed we ought; though he himself could not do so. It is deceptive to the reader to create a seriation beginning with eye spots as seen in unicellular organisms and call them, as does Duke-Elder (1958), the earliest stage of evolution."
Did scientist observed those transitional forms? Croft observed that" it remarkably similar. Indeed the basic features of the eye in different vertebrates are very much the same despite great variations in their mode of life and adaptation to habitat. Furthermore, unlike other organs such as the heart, there is no long evolutionary history with the eye. In essence the eye of a newt is as complex and fully developed as that of a man."
Just a reminder do not hold on the idea that natural selection formed those new organ because this idea is seriously challenge today. Isn't it good to hold only what is testable.? Certainly.
Edited by traste, : editing db codes
™ Version 4.2
(1)