I just finished Richard Dawkins’ book The Greatest Show on Earth, in which he explains the evidence for evolution. In fact, that’s the subtitle: “The Evidence for Evolution.”
I’ll mention here that I’ve long been a “believer” in evolution, although it turns out that my understanding of the theory and knowledge of the evidence were sadly lacking. Not to worry. The first few chapters corrected both of my errors.
The first part of the book explains the large concepts on which the theory of evolution is based: non-random natural selection of random mutations over a very long time. Evolution, as Dawkins points out multiple times in the first few chapters, is a slow process. There are no “revolutionary” changes over short time periods. It takes thousands of generations to evolve significant change, and even longer to evolve a new species.
After explaining the basic concepts, Dawkins begins on the evidence: how we know this is what has happened. As it turns out, the evidence for evolution is much stronger than I thought it was. We have radioactive clocks, DNA, tree rings, many different experiments, the fossil record, and many other sources of evidence, all of which agree on the fact of evolution. There might be disagreements on some particulars, but all of the evidence points to the conclusion that life on this planet evolved from one common ancestor.
Something that’s long bothered me about others’ reactions to science is their assertion that “it’s only a theory.” As a result, I was pleased to see that the title of the first chapter is “Only a Theory?” In it, Dawkins’ explains exactly what a scientific theory really is.
The Oxford English Dictionary, as Dawkins points out, gives two definitions of the word “theory:”
- A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is propounded or accepted as accounting for the known facts; a statement of what are held to be the general laws, principles, or causes of something known or observed.
- A hypothesis proposed as an explanation; hence a mere hypothesis, speculation, conjecture; an idea or set of ideas about something; an individual view or notion.
The “disconnect” when uneducated people say, “It’s only a theory,” is that they’re using the second definition of “theory”–the common usage that we hear every day. To them, a theory is an hypothesis or just idle speculation. A scientific theory, on the other hand, is much more rigorously defined. A scientific theory is the first sense of the word, above.
The theory of evolution is much more than idle speculation. It is an explanation of observed phenomena that has been confirmed by further observation and experiment. It is accepted by all serious scientists as accounting for the known facts.
The theory of evolution is no more and no less of a “theory” than the theory of gravity, the theory of continental drift, or Einstein’s special theory of relativity. All of these are based on observation and experiment, and serve as an explanation of the known facts.
One very important feature of a scientific theory is that it be disprovable. If you can find evidence that contradicts the theory, then at least part of the theory is incorrect. We’re seeing this right now with the recent experiments at CERN, where experimental results seem to show that some subatomic particles can travel faster than the speed of light, which contradicts Einstein’s special theory of relativity.
So far, all of the observations and experiments agree with evolutionary theory. There is no credible evidence to support any competing theories, and no evidence to contradict the idea that life on this planet evolved over billions of years, from very simple forms to the many and varied forms of life that you see today.
Dawkins spends some time (I think too much time) beating on what he calls “history deniers:” those people who, for one reason or another, deny the evidence for evolution. I’ll grant that I was amused by it early on in the book, but by the time I got to the end I was tired of hearing about it. There’s a fine line between showing how “competing ideas” don’t match the evidence, and ridicule. I think Dawkins crosses that line, and in my mind it detracts from the otherwise excellent explanations that he provides.
I sympathize with Dawkins’ desire to correct the collective ignorance that people cling to so dearly. If I didn’t run across it every day, I’d find it inconceivable that so many people deny the fact of evolution. It happened. It’s still happening!
I highly recommend The Greatest Show on Earth. If, like me, your understanding of the theory is based on the watered down explanation you got in your high school science class and the vehement denials that you get from others, then you’ll undoubtedly learn something from reading the book. It sure opened my eyes, giving a much better understanding of what the theory says happened, and the evidence that scientists use to back up that explanation.