It seems that creationism/evolution is the debate that just won’t end. More than almost any other scientific theory, evolution seems to be the hardest for people to accept. But why? Evolution is a theory that answers, at least in part, one of the most important philosophical questions of all time – Where did we come from? Why, then, isn’t evolution widely accepted? It seems to me that many people don’t believe in evolution because they don’t understand evolution. Perhaps they feel that sharing ancestors with chimpanzees somehow lowers their own importance in the world. They may think that accepting evolution means rejecting God. Their understanding of evolution may be that man evolved from some modern ape, which also isn’t true (Saying that man descended from some modern ape is like saying you descended from your cousin).
Whatever the misunderstanding is, I feel that it keeps people from accepting evolution. It may be naïve, but I think that evolution would be widely accepted if it were widely understood. This is one reason why teaching evolution is so important. So, in an attempt to clarify a few points I have put together a few of the most common arguments against evolution as well as my answers to those questions. In a later post I will present what I see as the most striking evidences of evolution.
1. Defining evolution
One of the core problems in the evolution debate may just be a poor understanding of the definition of evolution. A common definition from a dictionary says that:
There are a number of errors in that definition. First, an evolutionary change need not be gradual (and what does gradual even mean, scientifically?). Second, evolutionary changes are not required to be more complex. Third, the term “better form” is misleading. Evolution does not happen in a linear fashion with a desired, better end in mind. A more scientific definition would be:
2. Microevolution vs. Macroevolution
This is probably the number one complaint against evolution that I hear. It isn’t scandalous to say that bacteria will adapt to their surroundings, but the idea that man has evolved from some “lesser” species sends us to the courtrooms. Often I hear someone say:
“I believe in microevolution, I just don’t believe in macroevolution.”
Meaning that minor adaptive changes within a species can happen, but not major changes from one species to another. To me that sounds like:
“I believe in inches, I just don’t believe in miles”
The important difference between microevolution and macroevolution is time. Lots and lots of time. The same basic principles govern both processes – mutation, migration, genetic drift, and natural selection. These events over many, many generations result in genetic changes.
Mutation - Mutation is one of the processes responsible for evolution. Mutations are caused by radiation, viruses, mutagens (chemicals that cause mutations), as well as errors from cell replication. Mutations have been characterized and are known to happen. Imperfections in DNA encoding cannot be denied.
Migration - Migration is the movement of genes from one population to another. This is an important concept in evolution because gene frequency determines which genes will be passes on.
Genetic Drift - Genetic drift is the change in gene frequency based on random sampling. Genetic drift is more important in smaller populations.
Natural Selection - For some reason, this is the part of evolution that catches some people. If I told you there were two animals – One with a neck 4 feet long and one with a neck 4 feet 6 inches long – that both eat from a tree that is 5 feet tall. Which animal will have a better chance of surviving? Of course it is the one with a longer neck. It is just as obvious, then, that if the surviving animal has children it will pass on the genes for height. It’s offspring may even have a longer neck making it even easier to survive and pass on even taller genes.
3. Evolution is “Just at theory“
If you want to enrage a biologist, saying “Evolution is just a theory” is the perfect place to start. Here’s why – the scientific definition of theory and the colloquial definition are very different. The colloquial definition is an idea that someone has. Sometimes they have put some real thought into it and other times it’s nothing more than a fleeting thought – “I have a theory that…” is a common phrase. The scientific definition is much more rigorous. A theory is not just some idea, it’s defined as “a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.” A theory, then, is an explanation of some observation. This explanation must be tested to be correct, provide testable predictions, and is well understood. A theory does not become a fact, no matter how much evidence is given. So when scientists define something as a theory it is not to be taken lightly. It means that the concept is well understood, has been tested, and provides testable predictions. Evolution is not “just” a theory.
4. Evolution violates the 2nd law of thermodynamics
Some of the more “educated” opponents of evolution will say that evolution violates the 2nd law of thermodynamics. How? Well, the second law, as stated by Lord Kelvin, is:
Now, you may wonder what in the world that statement has to do with evolution. Another, less rigorous definition of the second law is:
“The entropy of a closed system can never decrease”
I suppose that statement may be as foreign as the first, so let me explain. Entropy is, in short, a measurement that describes how energy in a system is arranged. A system where energy is evenly dispersed has higher entropy than a system where energy is unevenly dispersed. Imagine a box with 10 particles. These 10 particles can be arranged in a number of ways.
The box on the left places all the particles at the bottom right, while the box on the right places the particles more evenly throughout. In terms of entropy, the box on the right has a much higher entropy than the box on the left. Another, even less rigorous definition of entropy is the amount of disorder of a system. In the boxes example above, the particles on the left are very ordered, while the particles on the right are disordered. The second law of theromdynamics, then, roughly states that a system will always move from the left box to the right – from order to disorder.
And this is what evolution deniers grasp hold on. They claim that since evolution can lead to a more ordered, complex system, that it breaks the second law of thermodynamics. This, of course, is not true. I’ll give two reasons. The first is a common rebuttal to the argument, the second is the actual truth:
1. The second law of thermodynamics states that the entropy of a closed system cannot decrease. Even if we define the system we are looking at as the entire earth, the earth is not a closed system (after all, the sun shines on the earth).
2. Order and disorder is, in the end, a very poor definition of entropy. It works in many cases to help describe entropy, and it is often correct. However, if you look at the actual definition of the second law it has nothing to do with order or disorder.
There are, of course, other arguments against evolution. I couldn’t describe them all in one post. In the next blog post I plan on presenting some of the most striking evidence I know for evolution. I’d love to hear your comments about this post until then.