Time and again, creationists have told me that ‘evolution is only a theory’. And so it is. The problem with this assertion is not with evolution, but creationists, and their absolutely blinding ignorance of science. Their understanding of the word ‘theory’ is based on the (very) colloquial meaning as in ‘that is my theory and I’m sticking to it’ or alternatively ‘that is my story…’. These everyday quotes are simply an assertion of what one believes or wants to believe, and is the sort of thing one might hear in a conversation between drinking companions.
What is a scientific theory? It is not a ‘story’ or a ‘belief’; it is an explanation of an aspect of the natural world based on a considerable amount of evidence obtained by observation or experiment, or both. Any theory based on such experiment or observation will make predictions about the results of subsequent observations and experiments. If those results are at odds with the predictions, then it is most likely that the theory will be jettisoned and replaced with a better one that explains the new results. This is how science advances. Creationists do not understand this. They maintain that the bible says the earth was created, and as evidence of that, they use the bible, in an example of circular reasoning so tight that it disappears up its own fundament. This is akin to me stating that the world was created when I woke up this morning at 7.36 am, with all memories, family and the stuff of my life in place, and when someone queries that, I simply tell them, but all the memories, family and other stuff were in place, so it must be true.
Perhaps one of the most well known examples of how science advances is shown by the understanding of gravity that began with Newton’s Theory of Universal Gravitation published in 1687. This, as most school students would know, states that a body attracts every other body in the universe with a force directly proportional to the product of the masses of both bodies, and is inversely proportional to the square of the distance between the bodies’ centres. It was an excellent approximation for the study of everyday observations at the time, and explained fairly well the movement and forces acting on masses in laboratories, and also gave a reasonable approximation of the movement of the planets. However, subsequent examination of the orbits of the planets showed there were some discrepancies, especially with that of Mercury. In addition, the angular deflection of light rays around the sun predicted by Newton’s theory was only half of what was subsequently observed. Einstein’s theory of General Relativity replaced Newton’s theory and it made predictions about the orbit of Mercury and the angular deflection of light around the sun, which were shown to be more accurate1.
This sort of thing also happened with Evolution. As I have written elsewhere, the concept of evolution was around for more than a couple of thousand years before Darwin and Wallace came up with a mechanism to explain how it happened2. As an aside, this is another thing that creationists do not seem to understand: the difference between the fact of evolution (as shown by the fossil record), and its mechanism (natural selection). One of the predecessors of the Darwinian theory of natural selection was that of Lamarck. It was he who developed the first cohesive mechanism of evolution. He stated that the environment induces changes in the mode of life of organisms, and these give rise to modifications in the development of their organs or the shape of the parts of the organisms. Darwin’s mechanism has it the other way around. There is a natural variation in organisms, and some of those are more suited to coping with that environment, and are more likely to leave offspring. Subsequent studies in molecular biology, genetics, homology, biogeography and observations of evolution in the laboratory, have shown natural selection to be essentially correct3.
I do get annoyed by the profound and wilful ignorance of creationists, and those on their periphery, but I will keep trying to inform them about reality, which is something they seem to know little about.