Part 1
Part 2
Part 3 of the Evolution series with Dr. Jay Wile and Marilyn Durnell.
Word count: 1,931
Estimated reading time: 7-12 minutes
As we said in the previous section, there is some evidence for the hypothesis of macroevolution. For example, consider some of the facts uncovered by geology. As you should have learned in a physical or general science course, geologists classify rocks as either igneous (the result of lava cooling), metamorphic (the result of rock being transformed under extreme conditions of temperature and/or pressure), or sedimentary (formed from particles of sediment). The sedimentary rock usually forms layers that are called strata.
Strata – Distinct layers of rock
In these strata, geologists find the preserved remains of once-living organisms. Those remains are called fossils.
Fossils – Preserved remains of once-living organisms
Each row in [the geological column] represents a set of layers of sedimentary rock. The rows on top are those sedimentary rocks closest to the surface, and those at the bottom are the deepest sedimentary rocks. Now please realize that the fossils listed in each of the rows are simply the ones that best characterize each layer. There are many other fossils in each set of rocks, but the ones listed in the figures are those that distinguish each set of layers from the others. When the rock layers are illustrated in this way, we say that you are looking at the geological column.
Notice the general trend in the geological column. As you go deeper in the geological column, the fossils seem to get more and more “simple.” Now we have already clearly seen that there is no such thing as a simple life form, but remember, we are talking about evidence for Darwin's hypothesis of macroevolution. Darwin and his early supporters did not have the benefit of microscopic analysis and detailed explanations of how organisms work. Thus, they did not really know that there is no such thing as a simple life form. Instead, they saw that the strata which were near the surface of the earth contained fossils of animals like horses, lions, and humans, while the deeper strata gave way to fossils of life forms like reptiles and small mammals. Even deeper, these fossils disappeared and only fossils such as fishes, squids, and trilobites remained. Darwin and his supporters thought that this progression of fossils went from “complex” organisms like human beings to “simple” organisms like squids.
Before we discuss how Darwin and his followers interpreted this geological column, we must make two important points. First, even though Figure 9.2 is a common representation of the geological column, it is not really what the geological column actually looks like! You see, 95% of all fossils that we recover are those of clams and similar organisms. There are, quite literally, fossilized clams in every region of the earth in nearly every layer of rock. So what we are showing in this representation of the geological column is really only about 5% of the fossil record. Thus, it is not a realistic representation of what the geological column actually looks like. Nevertheless, since the geological column is usually discussed in reference to macroevolution, the clams are ignored. Thus, any conclusions you make based on the geological column are, in fact, based on a tiny minority of the available data!
Second, it is very important to realize that the geological column is an idealized representation of the sedimentary rock and fossils that we see on the earth. There is really no place on the planet where you can dig and find every layer of the geological column as well as the fossils in those layers. Instead, you will find one set of fossil-bearing strata in one area of the world, and another set of fossil-bearing strata in another area of the world. These sets often contain some of the same strata, so by comparing many such sets of strata, Figure 9.2 is a representation of what the geological column might look like if you could find all of the strata and their fossils in one place. In other words, it is a theoretical construct that may or may not be accurate. It probably is a reasonable representation of the nature of the fossil record, but nevertheless, it is not pure data. That must be remembered when using it as evidence for or against any hypothesis, including that of macroevolution.
Now we can discuss how Darwin and his followers interpreted the geological column. To do that, we must discuss how the geologist Lyell (who influenced Darwin tremendously) interpreted it. Lyell said that the strata shown in the geological column were laid down sequentially over vast eons of time. Using his idea that the present is the key to the past, Lyell said that the strata seen by geologists were formed when sediments accumulated slowly over time. We see this happening today, he said, and it results in layers of sediment. Eventually, Lyell postulated, various chemical and environmental factors would take a given layer of sediment and harden it into rock. This would result in a single layer of sedimentary rock. As time went on, another layer of sediment would slowly accumulate on top of this layer of rock, eventually forming another layer of sedimentary rock on top of the previous layer. This would happen over and over again, eventually forming the layers of rock seen in the geological column.
Now, of course, all of this is speculation, but it is accepted by many geologists today as the way in which the rock strata in the geological column were formed. Well, if you accept this speculation as fact, then you are left to conclude something rather obvious. The deeper a rock layer is in the geological column, the farther back in earth's past it was formed. After all, since Lyell's process requires the lower rock layers to form before the higher ones can, the rock layers on top should be younger than the rock layers on the bottom. In fact, geologists even try to assign time frames for when these rock strata were supposed to have formed. Cambrian rock, for example, is supposed to have formed between 570 and 500 million years ago. The next set of rock layers (Ordovician rock) is supposed to have formed between 500 and 435 million years ago. Such numbers exist for every layer in the geological column. They are based on many assumptions, and it is not clear that they are accurate, but they are commonly used in reference to the geological column.
So, from the concrete scientific facts that sedimentary rock generally forms in layers and we find fossils in those layers, we develop a theoretical construct called the geological column. Then, when we add Lyell's speculation to the geological column, we are forced to conclude that the lower the strata in the geological column, the older the rock. If we further add more assumptions, we can even come up with how long ago such rock formed. If this is the case, then fossils found in strata that are low in the geological column are the remains of creatures that lived hundreds of millions of years ago. In the same way, fossils in strata near the top of the geological column must be the remains of creatures that lived in the more recent past.
Based on Lyell's speculation, then, Darwin and his followers argued that the geological column shows us that long ago, only “simple” life forms existed. That is why we see fossils of only “simple” forms in the lowest geological strata. As you look up the geological column, however, the fossils become more and more “complex.” This indicated to Darwin that as time went on, life forms got more and more complex. Well, Darwin argued, this is great evidence for macroevolution. After all, macroevolution predicts that life started out simple and, over eons of time and guided by natural selection, more complex forms of life emerged.
Now you have to realize that this conclusion is based on assumptions. You must assume that the geological column is an accurate picture of the earth's sedimentary rocks and the fossils found in them. You also have to believe that those rocks are formed as Lyell and many geologists today speculate: by the slow accumulation of sediment over eons of time. The geological column is evidence for macroevolution only if those two assumptions are right.
So the big question is, are those two assumptions right? The answer, from a scientific standpoint, is that we don't know. The geological column is probably a reasonable representation of the sedimentary rocks on earth. However, the issue of how those rock strata are formed is quite tricky. Since this is not a geology course, we do not want to spend a lot of time on the specifics. Instead, we will simply say that scientists have seen layers of sediment form slowly as a result of a process much like that suggested by Lyell. These sediment layers look a lot like “soft” versions of the sedimentary rocks we see today. Thus, it is reasonable to assume that sedimentary rocks can form that way. However, scientists have also seen that natural catastrophes like floods and volcanic eruptions can lay down many layers of rock virtually overnight. Geologists who have spent time studying the results of the eruption of Mount St. Helens in the state of Washington, for example, have documented the formation of a huge wall of sedimentary rock that has many strata in it, all in the span of about five hours.
Science tells us, then, that rock strata can be formed either slowly in a process like that suggested by Lyell or quickly as a result of natural catastrophes. So, if you want the geological column to provide evidence for macroevolution, it does. You simply have to assume that it was formed much in the way Lyell suggested that it was formed. If, on the other hand, you don't want the geological column to provide evidence for macroevolution, you can assume that it was not formed that way. Instead, you can assume that it was formed quickly as the result of one or more catastrophes. For example, we consider the major parts of the geological column to be the result of the worldwide flood that happened during Noah's time. An excellent book written by Dr. Steven Austin entitled Grand Canyon: Monument to Catastrophe uses the specific example of the Grand Canyon to provide convincing evidence that this is, indeed, the case. Of course, those who believe that the geological column was formed according to the speculations of Lyell also have evidence of their own, so the final answer is not clear.
Since, from a scientific point of view, we really don't know whether the geological column was formed according to the speculations of Lyell or by catastrophe, the data from the geological column is inconclusive. IF the geological column was formed according to the speculations of Lyell, then it is excellent evidence for macroevolution. IF, on the other hand, it was formed by one or more catastrophes, then it is excellent evidence against macroevolution. Creation scientists, for example, believe that the worldwide flood can easily explain most of the geological column. Thus, they believe that the geological column is evidence against macroevolution because it indicates that most of the fossilized organisms lived at the same time, in direct contradiction to the evolutionary view. Evolutionists, on the other hand, think that Lyell's speculations are the best way to explain the fossil record, so they believe that the geological column is evidence for macroevolution.
Stick around for "Part 4: Details of the Fossil Record: Evidence Against Macroevolution".
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