Everyday Evolution #2
Last weekend, we left the D.C. Metro area and headed a couple hours west to the caves of western Virginia. The geology of the Blue Ridge caverns is truly amazing. The ancient Grenville mountain range was thrust up over 1 billion years ago by the collision of the North American plate and the ancient continent of Baltica, which formed the ancient supercontinent of Rhodina. These mountains were eventually worn down torn apart by the subsequenct division of Rhodina, which opened up rifts in the earth’s crust from which lava welled up and filled in the valleys.
About 500 million years ago, the area was shoved under the ancient sea of Iapetus by plate tectonics and the remnants of the Grenville mountains were turned into granite under the intense heat and pressure. Around 300 million years ago, the region was again the site of mountain building as the North American and North African continents collided to form the supercontinent of Pangaea. The granite from the Grenville mountains, the igneous rock from the lave flows, and the layers of sediment from the Iapetus seabed (which recorded the Cambrian explosion), were folded and twisted into the patterns we see today.
These mounts would have been as grand as the Himalayas are today. But after 200 million years of erosion and the break up Pangaea, the modern Appalachians are all that’s left. The different layers sitting at different angles eroded at different rates, producing the ridges, mountains, and valleys we have today. The modern Blue Ridge represents the relative stubbornness of granite when threatened with erosion by the elements. Pockets of water within the mountains were formed when these layers separated form one another while the earth’s crust was being folded. As the mountains were thrust upward above the water table, the sub-terranian voids were drained. Water from melting snow and glaciers then dripped through the empty caverns forming the incredible scenery that attracts so many tourists today.
But the ecology of the caverns is even more fascinating than their geology. There is a white, sightless species of centipede that lives in the caves — that live only in THESE caves. Naturally, they are close relatives of the species of pigmented, sighted centipedes that live in the area — just the sort of observation we should expect to make if evolution were true. In fact, evolution predicts just this sort of thing. A species begins to take up residence in a cave, slowly loses it need for pigmentation or sight. It eventually moves deeper into the cave, becomes isolated from the ancestral population outside the cave, accumulates enough gene shuffling to prevent interbreeding with the other groups, and voilla — a new species is created.
If the closest living relative of this Virginia cave centipede was an Australian centipede, then evolution would have some ’splainin to do! But as it stands, everything is right where it should be. Biogeography is a powerful scientific model that only makes sense in light of evolution — because it is a necessary consequence of evolution. In the language of logic, evolution is both a necessary and sufficient cause of the observed patterns of biogeography: not only does evolution necessarily explain biogeography, but the theory is sufficient to predict general patterns of biogeography without ever leaving your house! That is the power of a useful scientific model.
So what is the creationist interpretation of our centipede? How could such an obvious data point on the trajectory of evolution be explained? Anyone who has ever had a swimming pool knows what happens when centipedes fall into the water — they drown. So presumably, Noah took a couple of centipedes on the Ark with him. Actually, he took a few more than that. Within the 2 subclasses and 5 orders of centipedes that populate the earth, there are about 8,000 distinct species of centipede. As if cruising around with that many centipedes on a boat for a year did not stretch credibility enough, the idea that a single species crawled off a mountain in Turkey and took up residence in a cave somewhere in Virginia — without stopping and leaving any evidence along the way is laughable. And by the way, without pigment or sight, it would have required a miracle to survive just the journey down from the mountain. But as long as we have an unlimited supply of miracles to throw at the problems created by a recent global flood, why not just open up a divine wormhole connecting Mt. Ararat with the Endless Caverns? Or why not temporarily give centipedes gills or flippers to survive the ocean? Or why not grant a special dispensation of “superevolution” so that millions of species can rapidly evolve from only a few created kinds? Or why not (insert your favorite unscientific speculation here)…?
Is this what science is reduced to for Conservative Christians? Speculating on what ad-hoc miracles are needed to preserve every physical detail of a biblical narrative – which itself is based on a miracle? In contrast to evolution, the story of Noah’s Ark is neither a neccesary nor a sufficient cause of the current state of affairs. Not only does it fail to explain what we see, but the model actualy predicts a biogeography that doesn’t exist! The population of Earth from species radiating from modern day Turkey should give a very distinct pattern of biogeography — but we can’t find THAT pattern. For instance, it is commonly known that the greatest genetic diversity of a species exists at its geographic origin. But there is nothing genetically significant about the flora and fauna of Turkey.
In mainstream scientific circles where reputations are based on integrity, something this obvious would be enough to falsify the Noahic flood as a scientific model (which is a bad assumption that Christians bring to scriptures). But not so in creationist folk-science circles, where you can just keep throwing miracles at your problems until they go away.
August 16th, 2008 at 6:59 pm
It’s a shame such a good post has gone without comment, so although I don’t have anything insightful to say, let me leave you with a simple thumbs up!
August 16th, 2008 at 9:09 pm
Thanks. This reminds me of the old days when I would post something that I thought was good and nobody commented. However, now that I know how to check my blog stats, I can see how many people are actually reading so I don’t get discouraged when I get no comments.
I’ll have the script for Lesson 15 (Education Series) posted soon for comment.
August 17th, 2008 at 10:44 am
Yes, Gordon, this was a delightful read and I have nothing to add or criticize — except to say that a thorough and thoughtful presentation of the Noah story from your perspective would be great. I know we’ve already discussed that a bit in this thread, so we don’t need to re-hash.
Anyway, thanks again for the post. I love beautiful evolutionary examples.
August 22nd, 2008 at 7:18 am
That’s a tough one. I think every ANE culture had a flood story. They seem to have been a very popular narrative framework for communicating information about the relationship between man and the gods. It would seem that the Hebrew tradition would be incomplete without a similar story that accurately reflected Hebrew theology - similar to how every ANE culture had a creation story that began with a watery formlessness and emptiness.
September 19th, 2008 at 3:19 pm
Okay, first of all, where did you dig up the long geological history of the Appalachians???
I’m finding geology more and more interesting. I used to think of it as the most mundane of all sciences (just a bit below biology:). I have a couple of college textbooks on geology and I am made several attempts to trudge through them though haven’t yet gotten enough motivation. I used to find biology dull, until I realized the reality of the vast history of common descent and then it became fascinating. Discovering the relationships and branching points of families of animals is extremely interesting. I think the same is now happening with geology when I consider the vast history of movement, sediment, metamorphism, mountain building, sea floor spreading, erosion, etc that made the earth the way it looks today.
Okay now to your post. I don’t think very many creationists will be impressed. First of all, “it is still a centipede!” Indeed, the very change you are suggesting is one they like to highlight, degradation of the dna, mutation leading to loss, namely that of pigmentation and eye sight. They would obviously agree that these centipedes are closely related to outside centipedes and show the functionless parts as how our dna is getting more and more corrupt. As for Noah’s Ark, anyone ignorant enough not to understand common descent already will have no problem thinking all modern day centipedes evolved over 4k years from just 2 pairs, I mean they look a lot a like. Plus, I don’t even think it is vogue anymore to put insects on the Ark. I believe in Woodmorappe book he claims that “creeping thing” are only reptiles and all the insects were floating around on vegetation mates. (ad hoc anyone?) . So anyway, it is a non-issue for the modern sophisticated creationist.
But that is not to say biogeography does not strongly evidence common descent and likewise common descent has amazing explanatory power of biogeography. I think you just need to think bigger. Australia is my favorite example. Here is an island that is isolated from the rest of the world for what, 100 million years. The mammals are all marsupial and therefor radiate and fill out the niches that become dominated by placentals on every other landmass. And filling those niches that converge on superficial outward morphology though clearly viewing the bone structure and underlining genetics reveals the history of the descent. Not only that but there is a fossil path through Antartica from south America (dating from the time these land masses were connected) with fossils of … kangaroos?, no, fossils of the most primitive marsupials. This fits common descent perfectly. This makes no sense for all animals leaving the ark at one place, why did only marsupials travel to Australia, and why is there this huge coincidence that they are all genetically more related to each other then their counterpart placental mammals? (sort of like they developed there…hmmmmmm).
But as for that hyper evolution, it would be interesting to see how far creationists do go. I mean, most people are ignorant enough of beetles that they probably group all the many species into one kind without much thought. But what about cat like things. Do they consider lions and tigers one kind? What about house cats. I mean, they are all so similar. I know they consider all dog like things one kind, and spew some absolute nonsense that wolves are the original least degraded of the kind, which degraded into coyotes, and then degraded down to dogs (despite the fact that genetic studies clearly show dogs and wolves share the most recent common ancestor).
Creationists always claim we don’t see one animal turn into enough, revealing off the bat they don’t understand common descent (every child is just a little bit different then any parent. Every alive species diverged from each other, no one species ever became another). But considering the actual form of descent, what I find interesting is that really a whole lot has not changed since we became mammals. Take a look at cats, dogs, bears, their underling bone structure is quite similar, and even we share it. We have eyes, ears, mouth, noses all in the same place. We all have the spine and rib cage, our four limbs and of course the famous mammal arm bone pattern. Looking at the great apes (us included) just at our bones, now we are really similar. Indeed among mammals, are bones are mostly just different sizes and proportions. It has been a 150 million years and we really haven’t diverged that far. The only examples I would exclude would be whales, who lost there back legs (most of the time:), and seriously moved the nose, and us, because we got these awesome brains and consciousness, thank you God.