 Evolution of the eye, the lens. Let's examine the lens of the eye, then decide if it was designed or evolved. What is the lens? It's the part of the eye that focuses light onto the retina. It is composed of three parts, the capsule, the epithelium and the fibers. The lens capsule is a basement membrane, a type of structure common in tissues that need a degree of adhesion to other tissues. It surrounds and protects the lens, but it's not unique to the eye. The lens epithelium is inside the capsule. It is a simple cuboidal epithelium, and like the same cells in the kidney and thyroid, it regulates the exchange of nutrients, fluids and salts. These cells are also not unique to the eye. Lastly, we come to the lens fiber cells. They derive from the epithelium as shown here. They are clear, long and thin, and some no longer possess nuclei or organelles. Now, these are unique to the eye. Let's focus on lens fiber cells. They are packed tightly and use gap junctions to generate lamina or layers. Note the hook and hole arrangement in this EM micrograph. So here's the question. Did the lens fiber evolve or was it designed? If it was designed, we should see irreducible complexity. That is, no part of the system is functional without all of the parts being intact. Specified information. The information to make the lens fiber must have been created by the designer for this structure. Fine tuning. The structure is specifically designed for the function it is being employed in. If it was evolved, we should see functional independence. The parts of the lens fiber have putative independent functions. Genetic homology. The information for making lens fibers must have arisen from existing information. Adaptation. The lens fiber should show evidence of prior alternative usage. So, is it irreducibly complex or is it functionally independent? Well, let's answer the simple questions. Do eyes exist that do not have lens fibers? Yes, lots of them. Does an eye without a lens work for vision? Yes, very poorly, but it does work. Are there proteins and lens fibers that are irreducibly complex? That's the interesting question. What proteins do we find in lens fibers? Well, 90% of their mass is a class of proteins called crystallins. Crystallins are highly soluble proteins that refract light and are responsible for the bending of light and lens. They are very stable proteins, seemingly designed as the perfect biological lens material. But are the examples of evolution or design? It turns out all the crystalline genes have evolved from other genes. We can identify which genes by their protein sequence similarities. Researchers studying crystalline in humans made a startling discovery. The protein that allows us to see and focus was being made an embryonic heart and kidney and in aggressively growing cancer cells. It turns out many of the crystalline proteins have other functions in embryology. Crystalline in mammals has strong homology to quinone reductase and alcohol dehydrogenase. Some of the subunits are still functional chaperonins, proteins that help fold other proteins. So, clearly not irreducibly complex. Specified complex D versus genetic homology is the information for making crystallins specified complex information or can it be found in animals without lenses? Well, let's do a protein-protein homology search on crystallins. Let's use the homology for crystalline alpha B. All vertebrates have about the same sequence. Invertebrates have some differences. Here's crystalline alpha A. Same thing, all vertebrates are almost identical. Invertebrates are similar but divergent. That's not even the good bit. Look what I get when I specify matches only in bacteria. And this too. In fact, there are over 200 matches for bacteria with crystalline alpha B. The top matches are all soil fauna for some reason, like nitricoccus here, the nitrogen-fixing bacteria, and root nodules. So the crystalline genes all appear to have come from duplication and divergence of existing genes. So, no on irreducible complexity. No on specified information. What about three specificity of forms? Is there any sort of prior art that exists for the lens? Is it optimally and universally designed? Well, first the obvious answers. Is the lens optimally and universally designed? Well, no. Many organisms possess lenses distinct from the modern vertebrate lens. Modern insects and ancient trilobite calcite eyes show different lens architectures. So let's note a universal optimal design. Is there any structure of the eye that does not exist elsewhere in the human body? Only the lens fiber cells. The capsule, as we mentioned, was a standard basement membrane. The epithelium is a standard simple cuboidal epithelium. Is there a prior art to the eye? Well, yes. Certain unicellular organisms possess an eye-spot organelle. They are composed of a region of photoreceptor shaded by red pigments, making them blue-green specific. The heterotrophuglena is shown here. Okay, is there a prior art to the lens? Yes, the waxy cuticle epithelial cells in plants, and some algae are intentionally transparent. So is the lens of the eye designed or evolved? The evidence is clear. How do the evolution of the lens likely occur? Well, here's a likely scenario. Start with low expression of ADH in all tissues. Always expressed at a low level, no matter what. That's what we call constitutive expression. This is typical for all genes not under tight control. The constitutive gene product comes under tight control by a regulatory pathway related to eye development. The constitutively expressed gene, ADH, becomes tightly controlled as part of development. There is a selection for proteins that do not interfere with optical transmission. The constitutive gene duplicates and diverges, resulting in a normal non-lens form and a specialized form in lens development, now an early crystalline gene. There are now two different gene products subject to different selection pressures, but still structurally similar. Now, why does any of this matter? Because every year, thousands of babies are born with cataracts due to genetic defects. Understanding where these defects come from, what genes are involved, and how animal models are applicable may help us diagnose and treat babies born with genetic defects. It does matter.