Darwin's Big Problem
Darwin's Big Problem
Darwin's theory of evolution is a cornerstone in our understanding of how and why organisms change. However, new discoveries in the world of science have caused some problems for his theory. The word 'evolution' comes from the Latin word evolvere, which means to unroll. When one thinks of the classical Darwinian idea of evolution this is a very fitting root. The slow, constant rate of change that Darwin proposed for his theory of evolution is very much like someone unrolling carpet. The carpet is unrolled straight and consistently, always the same width, traveling the same direction. Smooth and even are two great words to describe the theory of evolution and the act of unrolling a hypothetical carpet. However there is one big problem with this idea, and that is the geologic record. Instead of seeing a nice straight, even line, we see big splotches. Instead of someone unrolling a carpet, we see something more like someone drawing a line, but this is someone with an unsteady hand who does not know how to use an ink pen. The line varies in thickness and is littered with ink splats. This is what the geologic record looks like, and it does not seem to concur with Darwin. The term punctuated equilibrium has been produced to explain this geologic phenomenon. In this paper I will argue that Darwin's original theory of evolution is flawed in that organisms do not just slowly evolve over time, but often evolve together very rapidly. While organisms may go through periods of slow change, Darwin's original theory cannot alone explain how organisms evolve. Punctuated equilibrium better demonstrates how organisms evolve and explains the anomaly of the geologic record.
Darwin's theory of evolution centered on the idea of gradualism, or slow change over time. He believed that organisms continually changed very slowly over long periods of time. He could support this theory quite well because of the work he did with pigeons. Darwin discovered he could alter traits within pigeons over several years through selective breeding. These were small, slow changes, therefore it made the most sense that this was how all organisms changed. He had physical proof and had not observed anything else. However, he was aware of a few issues.
The reason punctuated equilibrium is Darwin's big problem is because it was an issue when he was publishing his theory. A chapter of his book is dedicated to issues and inconsistencies in the geologic record. He states that “if numerous species, belonging to the same genera or families, have really started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection”(243) . . . “this was a sore trouble to me, adding as I thought one more instance of the abrupt appearance of a great group of species”(245). Not only did Darwin recognize that this could be a challenge to his theory, he even feared it. Every new piece of evidence that supported these sudden appearances caused him grief. In the end I think he hoped it would just go away. He blamed “our ignorance of geology”(246) as why he could not resolve this occurrence and further support his theory. Darwin was right, the geologic record is incomplete. While he did address this issue with his theory, it is a rather weak explanation.
After Darwin's time, geologists were still unable to provide evidence for his theory. Instead of providing proof, more and more evidence seemed to point toward the fact that the Cambrian Explosion and Permian Extinction, along with many other periods, demonstrated an evolutionary pattern in which animals rapidly evolved together and rapidly went extinct. “There is a good deal of evidence that biological evolution is not gradual, but episodic, with long periods of stasis interrupted by bursts of rapid activity” within single species and “across taxa”(Sneppen et al 5209). Darwin may not have been completely correct in his theory, organisms probably do not slowly and steadily evolve over long periods of time. This idea was a key point in his argument, however Darwin was not all wrong and is certainly not now any less important. Sneppen describes Darwin's theory as the “atomic theory”(5209) for all evolution, and I quite like that. Darwin is where the base of evolutionary thinking begins and from there one can expand.
One can see why Darwin chose this idea of gradual change for evolution, he witnessed it himself. He was able to alter the characteristics of pigeons in just a few years. These were small, slow changes that he could produce. It is easy to see why he chose this model, he had the evidence for it. It is understandable that he hoped the geologic record was just too jumbled to be very useful. For him to make the geologic record work for his theory he would have had to come up with a complicated story to explain why it was the way it was. That probably would have detracted from his core theory of evolution so it was easier to just accept that it was an anomaly. Darwin did not do a bad job. However, I believe that punctuated equilibrium is a better theory than gradualism and I base this judgment on the principle of Occam's Razor. Occam's Razor is a principle that states that the hypothesis that makes the fewest assumptions, or has the simplest story, should be chosen. Darwin demonstrated his theory of gradualism with his pigeons. While the geologic record is incomplete, it always support punctuated equilibrium and never appears to support gradualism. Punctuated equilibrium is the easiest story to explain. For the story of gradualism, one must create a complicated story to explain why the geologic record does not seem to support it. In Darwin's time, gradualism was the easiest story, but now I think punctuated equilibrium has been proven to be the easiest. The simplest explanation is the best answer.
Darwin, Charles, and George Lewis. Levine. The Origin of Species. New York: Barnes & Noble Classics, 2004. Print.
Sneppen, Kim, Per Bak, Henrik Flyvbjerg, and Mogens Jensen. "Evolution as a Self-critical Phenomenon." Proceedings of the National Academy of Sciences of the United States of America 92.11 (1995): 5209-213. JSTOR. Web.