This article is old now; but it indicates that the "mystery" of eye and wing is no more than a red herring. Evolution is as certain as the fact that the moon is not made of cheese. Please understand, however, that this does not invalidate the concept that the unknown might hold mysteries that point to us being the purpose of another. Who knows? However, evolution is not mysterious in and of itself. We see it in every stage of the embryo/fetus; we see it in the fossil record; we see it in the laboratory.
We now know that there is an eye gene we share with a one celled creature: the latter operating as a light sensing mechanism. Yes, less than half an eye is valuable and intelligible--much much less.
Disturbingly, we see it in the relentless push of "Super" bacteria to use humans for their food and reproduction. Our current pace of advancement is far slower than theirs. One day they will probably get a great number of us...
Evolution is atacked by "creationists" because it interferes with a God belief called Yahweh. For the rational person who does need need to limit his/her "spiritual" sense to ancient myths of storm gods...evolution offers no impediment to the human urge to conjecture, invent, and hope. Indeed, it is that very sense of commune with Nature which is sufficient encounter to satisfy the sense of comfort, home, and "god" for many people. For such people, evolution itself is sometimes thought to be "intelligent".
Teilhard was a paleontologist and actually worked it into a mystical belief system rather than fighting what was only too too obvious. Beyond that and from a slightly different angle we have the ID people attacking evolution. If it should ever evolve beyond a criticism and take on some theoretical cohesiveness, it would be worth more than a passing interest...
It is the clinging to such fanciful, child-like, and impossible stories as the Gilgamesh flood/ark/release the doves myth which prevents people with perfectly good eyes from seeing past their own dark shadow.
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Creationists are very fond of the argument that evolution literally won't fly - especially in the case of birds - because "half a wing is worse than no wing at all." The implication is that in the evolution of arms into wings, intermediate stages would be produced which would be usable neither as arms nor wings. A similar argument is leveled against the idea that the human eye evolved: half an eye would be useless, they claim.
When creationist big-wigs use such arguments, they are al-most certainly intending to deceive, for they know perfectly well that vast amounts of material have been written developing step-by-step scenarios for the evolution of both eyes and wings - scenarios in which every stage in the evolution of the eye is useful, and every step-in the evolution of wings confers a survival advantage upon the so-called proavian, the bird-to-be.
The Evolution Of Flight
Although some very famous ornithologists have thought otherwise, I am convinced that the majority opinion is correct: bird flight began in the trees, not on the ground. Having evolved from small, two-legged dinosaurs, the proavians were arboreal bipeds. Proavis used its "hands" to climb‚ into trees in much the same way that young hoatzins - primitive South American birds - today still use their finger-remnants to scuttle back up to their nests if they fall or jump out of them. But the major mode of proavian locomotion while in the tree, I believe, was bipedal hopping.
Hopping short distances from branch to branch presented few problems for Proavis. (Proavis, keep in mind, was a precursor of birds, not a prehistoric rental car!) But jumping greater distances, especially from higher to lower branches, created a serious problem. Upon landing with its feet on a target branch, momentum would have tended to rotate the animal forward on the branch - making it end up hanging from the branch upside-down! The situation would be even worse if the branch were flexible instead of rigid. Suitable braking, by flailing the arms, would have helped to prevent this - as readers can easily demonstrate for themselves if they set up two chairs several feet apart and then try to jump from one to the other, without flailing the arms, and without falling off or tipping over the target chair. As the distance between chairs increases, the experimenter's arm reflexes will quickly demonstrate how important arm-flailing must have been to the bipedal branch-hopping proavians.
The lengthening and fraying of reptilian scales to form feathers would have conferred a great selective advantage upon such creatures as I have envisioned. (Many birds still retain reptilian scales on their legs, remember, and even the barnyard hen occasionally sports structures which are part-scale, part-feather.) Body feathers may very well have existed long before flight evolved as a means of thermal insulation allowing the animal to maintain the high body temperatures needed for active life in trees. Longer feathers, such as wing and tail feathers (often the first non-down feathers to develop in the young of songbirds) first evolved not for flight, but as a means of improving aerial braking and balancing capability as Proavis hopped and parachuted from branch to branch.
The larger surface area provided by the feathered limb would allow for more effective "air-braking," and would make possible later reduction of the inertial mass of the arms and other parts of the body - a handy thing still later when active flight developed. Proavis probably behaved a lot like the previously mentioned hoatzin which, even as an adult bird capable of clumsy flight, seems to spend more time flapping its wings to keep from falling off branches than it does in active flight!
Among the many combinations and sequences of muscle and joint movements involved in air-braking were those needed for the power-stroke and other flight movements. It would only require a bit of selective shaping to make the power-stroke anatomically less stressful and more powerful. The transition from flapping, parachuting and braking, to active, flapping flight would have been very gradual and easy, without any maladaptive intermediate stages. The oldest avian fossil, Archaeopteryx, by the way, is a marvelous connecting link between two-legged dinosaurs and modern birds. It had a long, lizard-like tail, teeth, clawed wing-digits still usable for climbing, and many other reptilian skeletal features too numerous to mention here. In fact, the only thing bird-like about it was its feathers. Of course, the creationists deny this. After decades of insisting that Archaeopteryx was a perfectly complete and genuine bird, they now are echoing the off-the-wall claims of the astronomer Fred Hoyle that all the fossils of this creature are hoaxes. No matter which museum the fossils are in, we are to believe, the curators have chiseled feather imprints into the limestone!
Flight has evolved independently a number of times in the history of the animal kingdom: among the bats (mammals), among the birds, among the pterosaur reptiles (pterodactyls and their cousins), and among the insects. In each case, natural selection has used different means to achieve the same end.
In the three vertebrate cases mentioned, wings have evolved by alteration of the anterior paired appendages (the "arms"), with differing emphasis on which parts of the appendage will produce the major part of the wing. In the case of birds, almost all the parts of the arm figure prominently in the structure of the wing. In the case of bats, the bones of the hand and fingers account for the major flight surface. (A bat flies by flapping its hands.) In the pterosaurs, a single finger became extremely long and served as a strut along which a sail-like wing of leathery skin was stretched.
In the insects, however, there was no preexisting locomotor appendage which could be modified for flight, and so wings originated in a manner quite differently than in the vertebrates. The protowings of insects apparently had nothing whatsoever to do with locomotion, let alone flight. Rather, they began as flat, horizontal outgrowths from the upper surface of the middle section of the body (the thorax). What was the function of these plate-like structures? It is now all but certain that these structures were primitive solar-energy collectors -- although thin platelike body projections could also have helped preflight aquatic insects wind-sail across the surfaces of bodies of water.
Insects are "cold-blooded" animals, and tend to be lethargic or inactive when the temperature of their environment is low. If, however, a way be found to increase the amount of solar energy absorbed, it becomes possible to warm the blood and, by pumping warmed blood through the body-core and nervous system, to remain active at temperatures otherwise too cold to allow insect activity. The simplest way to increase the amount of solar energy absorbed is to increase the body surface area, while increasing body volume as little as possible. Any flat, horizontal outgrowth from the upper surface of the body will suffice, and a variety of such structures are known in both living and fossil insects. In the case of those outgrowths which were destined to become wings, the structures were located on the three thoracic segments of the body, the same segments on which the walking legs are located.
Any mutations increasing the size of these solar-collectors would tend to increase the probability of survival, by increasing the amount of blood-warming energy absorbed, and we would expect to see these structures increase rapidly in size. A further advantage would be gained by animals with mutations causing superficial thoracic muscles to become attached to the base of these solar panels, allowing them to be bent or arrayed at various angles to the sun and, thus, to modulate the amount of energy absorbed. Once such moveable solar panels had increased to a certain size, they would begin to serve as protowings. At first the protowings would be used only for gliding flight and to assist in wind-dispersal of the animals into new environments. But natural selection would rapidly increase muscular control and motility of the structures, and full-fledged wings would result.
That this is indeed the way that insect wings evolved is supported not only by computer-modeling studies, but also by studies of both living and fossil insects. Many living insects still use their wings as solar-energy collectors, pumping blood into the veins of the wings (often by means of special auxiliary hearts) and returning the heated blood straight from the wings to the brain. Even though wings have added flight to the behavioral repertoire of insects, wings still retain their primitive thermo-regulatory function.
(see rest of article and also...
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