No, its not Illustration Friday — a website that encourages people to draw something once a week. In reaction to the unending, uneducated, and overly vocalized mantra of creationists heard in school board meetings across the country, I’m launching “Evolution Friday”. My intent is to combat the their “creation science” drivel. As a veteran scientist — hmm, can I call myself that? A war “veteran” is someone who served in a war — even if only for a short time. I have served in science for six years, so I think I ought to qualify. But still, it sounds far to pretention to call myself “veteran”. How about “former”?. As a former scientist, I’ve seen first hand a lot of things that confirm the theory of evolution. It seems the least I could do is share it with you.
Today’s Evolution Friday Topic : Convergent Evolution.
As a student of Ichthyology, I spent a fair amount of time in the lab classifying fish species. Fish inhabit a wide variety of environments: Open ocean, shorelines, estuaries, rivers, streams, lakes, caves and even some extreme environments like arctic waters where the temperature is below freezing. Carl Linneaus (he was working in plants at the time, but his work applies to all living things) noticed that some species were quite similar to one another (such as two species of Oak), but were different than other species. He created a system called Taxonomy, by which he organized species based on these similarities and differences.
One interesting thing about Taxonomy is that something that seem quite similar are in fact quite different. For example, consider sharks, rays, walleye, and flounder. Superficially it seems that the shark and walleye are more similar based on their overall shape. Rays and flounder, on the other hand, while similar to each other, have a much different shape than the shark and walleye. So it would seem that the shark and the fish should be closer together taxonomically, as should the ray and flounder.
But upon closer investigation, it becomes clear that actually the shark and the ray are more similar to each other than either is to the walleye or flounder. And the walleye and flounder are quite similar as well. The shark and ray both have cartilagenous skeletons, whereas the walleye and flounder have bony skeletons. The shark and the ray both have seven gill slits, whereas the walleye and flounder have a single gill structure covered with a bony operculum. The walleye and flounder have different kinds of teeth than the shark and ray. Only the walleye has a swim bladder. Walleye and flounder have scales, the shark and ray have denticles. On a molecular level, the shark and ray share a greater percentage of their nucleic acid sequences than do the flounder and walleye.
This presents a riddle for Creationists. Why are similar functions “designed” in different ways. Both the ray and the flounder are bottom dwellers that move about using vertical oscillations of their limbs, but their structural make-up are radically different. Furthermore, why is the flounder built with a bizarre twisted face, so that one eyeball isn’t wasted staring at the mud? Wouldn’t it make more sense for a designer to build a flounder with its eyes evenly spaced on top? Why would a designer reinvent muscle fibers, skin coverings, neural circuitry, etc. to achieve the same purpose?
These strange observations are easily explained by the theory of evolution. The flounder and they walleye are descended from a common ancestor that looked much like the walleye does today. However, in one lineage, flounder’s ancestors found a good living was to be had by hiding on the sea floor. Eventually random changes accumulated that made flounder’s nearer ancestors more successful at that; it learned to swim on its side, its face started to twist, etc…. A similar process happened with the ray. An ancestral fish, probably lived in a way similar ot the dogfish (a kind of shark) does today — by skulking around on the bottom. Fins got longer and longer, as fish with bigger fins could skulk better. Eventually the fish looked and swam more and more like a ray.
This process by which two species acheive similar functionality via different processes is called convergent evolution. For the flounder and the ray, each acheive the abilities so hide on the bottom of the ocean and swim with vertical oscillations — but acheived them through separate processes. The natural world is filled with other examples of this process. Evolution explains it; creation science cannot.
