I was thinking recently about the common attempts to explain what a scientific theory is by pointing out that gravity is “just” a theory. This is, of course, usually in defense of people who say that evolution is “not a fact, just a theory.” I was thinking about how the concept of evolution, in general and abstracted from a biological context, is a very logical idea that doesn’t actually need evidence in order to make sense. This differs greatly from the theory of gravity, which only makes sense in light of observations. Thus, evolution makes more sense than gravity. Let me explain.
Both concepts were developed in light of observation. For gravity, people recognized that things always fall when dropped. Eventually it was found that all objects fall at the same rate, and then realized that there was a force between all objects, dependent on mass, that pulls them toward one another from very great distances. The simple equation describing the gravitational force between two objects can then be used to predict what the interactions between those objects will be like. Gravity is a beautiful example of the scientific method, where we start from observation, come up with rules, and then test those rules against more observations. On top of that, the theory has been fine-tuned over a few centuries to be able to describe more and more observations. The important point I want to make here is that, in the absence of observations of falling objects, gravitational theory makes no sense at all. The equations are useless unless you observe and take measurements of moving objects. The theory only applies to observation.
So how does this contrast with evolution? Like gravity, evolution was a theory developed by many people over many years. Darwin was not the first to come up with it, he was just the first to pile up so much evidence for its occurrence in nature. My claim is, however, that the evidence isn’t necessary. Why is this? I’ll first state that evolution is not specifically a biological concept. It has to do with pieces of information that copy themselves and are prone to some amount of error. Any self-replicating information can and will evolve.
So why did Darwin need so much evidence for evolution? He didn’t. He needed evidence that evolution occurs in biology. This is a different issue entirely. There was a key biological concept that Darwin did not know, the genetics of heredity, which by itself forces biology into an evolutionary process. This is why Darwin needed so much to show that evolution happens in biology- he didn’t have the mechanism that would make it a matter of logic instead of overwhelming evidence. Fortunately, now we have both.
This probably isn’t clear yet, and I’m having a little trouble organizing this argument, so let me next go into how evolution works as a general concept.
So what do we need for evolution to occur? First and foremost we need discrete packets (quanta) of information. This information can be in the form of computer code, colors, DNA sequences, or anything else. Second, the quanta must have some variation. Third, there must be a way for these quanta to be copied (heredity). Either they copy themselves (reproduce) or some outside agent copies them. Lastly, and this is the big one, some quanta will be more likely to be copied than others because of their variation (or, in biological terms, will have greater fitness).
In the case of biology, the bases in DNA are our quanta. The DNA between any two organisms is quite likely different, there are mechanisms for copying and passing DNA to further generations, and some DNA causes the organism that contains it to be more likely to leave copies of that same DNA. So all the thing necessary for evolution to occur are there. In fact, if you have these things evolution will occur.
Now that I have presented the things necessary for evolution, it seems like a good time to define it. Evolution, in biology, is defined as “a change in the frequency of alleles in a population.” This definition will mean nothing to anyone who is not familiar with genetics, and the whole point of this post is to explain that evolution is not a biological concept. So, if we do away with genetics and generalize the definition, we get something like “a change in the proportion of a variety of quanta within a group of quanta.”
For example, let’s say we have some colored squares that have only two heritable traits: shape and color. Each square thus contains two quanta of information. These squares can also make copies of themselves by passing down these quanta. To keep things simple, let’s make our squares asexual (they don’t need a partner to make offspring). So to reproduce, a square simply divides in two and then each new half grows until it is the same as the original.
My hypothetical square population contains 5 red and 5 blue squares. They start reproducing. Will evolution happen?
The only piece of information I need to add for you to be able to answer this question is that reproduction rate is constant and not influenced by color or shape. Can you see that the answer, then, is that evolution will not happen? Refer to the definition. We must have a change in frequency of some quanta for evolution. Our two quanta are shape and color. The color varieties start out equal and will increase equally, so the ratio is always 1:1. There is no variation in the shape quality. Thus, no frequencies will be changing over time.
Now let’s change the starting population to 5 red and 4 blue while changing nothing else. Does evolution occur?
These squares will exhibit exponential growth, following the equation total=N*2^t, where N is the starting population and t is the time. So you can see the ratio will be (5*2^t)/(4*2^t) and so does not change over time. So evolution will not happen.
Now what if blue multiplies twice as fast? You can easily see, even without the math, that blue will quickly overtake red and eventually red will be an insignificant part of the total population. For anyone who likes the math: you have red=5*2^t and blue=4*2^2t. You can simplify it if you want, but just consider what happens as t gets large and larger. The ratio of red divided by blue will get smaller and smaller, disappearing as t goes to infinity. Now evolution has happened.
So, to repeat, all you need is variable information that can copy itself and then evolution will happen, as can be shown mathematically. This is true regardless of what the information is.
For biology, we have variable information that is heritable and has an effect on how many offspring the carrier leaves behind. No one, not even creationists, can reasonably argue against this. It has been known for a long time, has been shown over and over again in experiments, and has been observed in real time. What people often don’t realize is that this automatically means that evolution happens. We have everything that is required, and evolution is simply the process that occurs when those things are present, nothing more. So we don’t even need the evidence for evolution to know that evolution occurs.
And that is why evolution makes more sense than gravity.