The evidence described in blogposts 10-14 brings us back to the question of how it is that bacterial flagellae, the eye of a fly, the engineering feat that is the flight feather of a bird, and the human hand and head, in all their diversity and complexity, could have come about within the framework of natural selection without necessarily requiring an overseeing Creator. The Jon McNaughtons and the Intelligent Design proponents insist that evolution could not have produced such incredibly complex results. There is a wealth of published evidence available to support the scientific answers that evolution did just that. In this blogspot, we will review the data regarding bacterial flagellae and the amazing variety of eyes found in the natural world.
Consider first the bacterial flagellum, a study in complexity in miniature: Escherichia coli, a common gut bacterium swims about using a tiny tail that spins in a complex and integrating fashion which is made up of several dozen different proteins. Creationists insist that that tail could not have evolved bit by bit, but rather had to have appeared in its present extremely complex form as an act of Creation. In fact, scientific evidence shows that the flagellar proteins were assembled from simpler parts. The flagellum is built by a kind of pump that squirts out proteins, a pump nearly identical, protein-for-protein, to one found in many disease-producing bacteria. Those pathogens, however, use their pumps not to make a tail, but rather as a priming mechanism for a molecular syringe that injects toxins into host cells. It has been proposed that the parts of E. coli’s flagellum came together step by miniscule step over millions of years. It started with a syringe-like pump, acquired a long needle, then a flexible hook at its base. In time it linked to a power source, another kind of pump found in the cell membranes of many bacteria. Once it was equipped with a “motor”, it became able to spin, and the needle evolved into a propeller. The result was that the microbe had new and complex mobility. There are scores of different flagellae in different bacteria, all the results of differing avenues of natural selection. Although E. coli makes only one kind of complex tail, it also carries the remnants of genes capable of making other types of tails.
And consider the marvelous eye: Darwin, in awe of the exquisite construction of the eye, which would be useless if it were not perfect, said, regarding the natural selection producing the eye, “[It] seems, I freely confess, absurd in the highest degree.” Other early evolutionists, taking a less defeatist point of view, thought that eyes had to have evolved independently many different times and in different ways. Modern research, however, indicates that eye-building genes evolved only once in an ancient animal and then other genes under control of those primordial eye genes produced eyes which over time changed from simple to increasingly complex. What follows is a synopsis which only describes a limited sketch of the evolution of eyes. For more in depth presentations, the reader is referred to Richard Dawkins’s, Climbing Mount Improbable, Chapter 5, pp. 138-197, W.W. Norton & Company, New York and London, 1996, and Sean B. Carroll’s, The Making of the Fittest-DNA and the Ultimate Forensic Record of Evolution, Chapter 4, pp. 92-113, and Chapter 8, pp. 193-203, W.W. Norton & Company, New York and London, 2006.
Modern anatomists concede that the eye is, in fact, far from perfect, despite all of its wondrous ability to allow animals to see, and it would seem very much out of character for a perfect Creator to create an imperfect eye. The retina is too loosely attached to be safe from a blow to the back of the eye; its light-gathering cells, for some inexplicable reason, point inward towards the brain instead of the more logical orientation of pointing outward towards the source of
light. The optic nerve starts in front of the retina and then passes through it en route to the brain producing a blind spot. Evolution has blunders, but still produced an eye; a Creator would scarcely have been the author of errors. Evolution has produced different eyes from the primordial eye genes and their myriad changes. The differences in eyes are profound. The process of evolution proceeded from simple to complex because of the extreme adaptive value of improving vision with more survivors among populations that could see more clearly or with improved color vision. Two photocells capture more photons than one, three better than two, and so on. Photocell arrays of membranes are lined in layers, each layer containing vital photon-trapping pigment; a human photo-cell has around ninety-one layers with the same biological logic: 91 layers capture more photons than 89 layers or 45 layers, and so on. For each of these evolutionary developments, even one is better than zero.
Human eyes have a single lens and retina. Fly eyes are made up of thousands of tiny columns, each capturing light with ciliary photoreceptor cells. Insects and other invertebrates use rhabdomeric photoreceptors, cells with distinctive chemicals. When underlying genetic functions that build photo receptors are studied, insects and humans are found to use the same genes, genes that cause embryonic photo-receptors to capture light, using opsin molecules. It is evident to evolutionists that almost all animals’ photoreceptors evolved from a single cell that eventually split into two types—rhodomeric and ciliary.
It is also presumed that some animals carry both types of photoreceptors. Recent modern science showed that rag worms, aquatic relatives of earthworms, have rhabdomeric photo receptors in their eyes and ciliary photo receptors hidden in their brains where they appear to sense light, not for seeing, but to set the rag worm’s internal clock. It would appear that the common ancestor of most current animals had a basic complement of genes for building organs for detecting light, much like what is currently found in salps, gelatinous sea creatures. Salps possess pits lined with photo receptor cells, adequate only to sense light and to tell the direction from which it comes. Still, one is better than zero. These simple receptor structures came from the same set of genes that produced fly and human eyes.
The lens of the eye is made of up transparent proteins called crystallins, which bend light. Crystallins existed in creatures well before they became part of an eye. Sea squirts use crystallins to sense gravity. The same genes that are found in flies and humans likely mutated to give the crystallins new and different functions, and after myriads of changes occurring over eons of time, became the astoundingly complex eyes of modern animals. Limpets have basic eyes in which light-sensitive eye structures are covered with protective transparent cells. The structure is too basic to form an image, but allows for sensing light. Beyrich’s slit shell has a deeper eyecup which allows for information about the direction of the light source to be transmitted, but still it is inadequate to produce an image. The Chambered Nautilus has a fluid filled cavity surrounded by a light sensitive layer that can be called a simple retina. It is connected to an optic nerve. A small gap at the top of the Nautilus’s eye chamber acts like a pinpoint pupil or camera that focuses light on the rudimentary retina and allows for the formation of a dim image. The Nautilus organ is every bit an eye. Murexes are medium to large sized predatory sea snails. The Murex eye has a lens, cornea, retina, and its fluid cavity is fully enclosed. Light is focused by the primitive lens on the enclosed retina to create a slightly sharper image. The Common Octopus has a distinct cornea and lens, a clear-cut retina enclosed in a tightly sealed fluid chamber, and a colored iris. The lens is capable of focusing light to produce a considerably clearer image. The scallop’s primitive blue eyespots capture light with a mirrored surface, and the complex camera-type eye of vertebrates from sharks to sunfish to birds to humans evolved from the same type of basic light catching device.
The New Zealand tuatara, or Sphenodon, which looks like an iguana, but is a reptile unlike any other in the world, or any other vertebrate, for that matter. It is a living fossil with a basic skeletal structure and skull shape almost identical to that of tuatara fossils dating back to a period before the rise of dinosaurs. Its organs and traits are closer to the evolutionary baseline than comparable structures in other animals, such as teeth of the same design as dinosaurs, and the possession of a remarkable eye. The tuatara has a third eye at the top of its skull, a poorly understood pineal eye, which is found in only a very few reptile species and which vision researchers believe harks back to one of the original eyes found in nature—basically a few light sensitive cells on a stalk.
The genes that produced these many kinds of eyes evolved from a closely related common ancestry. The concept that all the different types of eye structures and functions evolved independently has been demonstrated to be incorrect. Evolutionary theory adjusted to the concept that each eye did not have to start from a wholly different beginning, and certainly not from multiple eyes being created in their final modern structure and function; rather changes occurred in basic common elements. Duplication in genes allowed for two genes to evolve in different ways to result in the same result—seeing and understanding the information coming in from a perceived image. continued…