Saturday, January 30, 2010

Yes, Evolution Really is a Proven Fact

I do not need to be convinced of the fact of evolution. I’ve known that organisms have evolved ever since I took biology in high school all those decades ago. I also know that not everyone shares my conviction that evolution has happened.

Oh, I know, even the most ardent creationist admits that evolution happens up to a point, within a species. But they go on blindly denying that one species can evolve into another.

Although I needed no convincing, I decided to read Richard Dawkins’ newest book on the subject, The Greatest Show on Earth: The Evidence for Evolution. I’m not even completely finished with the book yet, but I’ll have to say, if I were ever a fence sitter, I would no longer be straddling. I have taught biology in high school and middle school for years, and I know all the standard lines of evidence commonly taught to students. But I must admit I did not know how deeply the evidence supporting evolution went until I started reading the book.

Forget fossils. Yes, they still provide grand evidence supporting evolution. But, as Dawkins states, fossils are neither the only nor the best evidence for evolution. In fact, evolution would be on solid ground even if not a single fossil existed.

Take the DNA evidence for example. I’ve taught genetics as part of my science class as long as I’ve been a teacher, but the story of how DNA provides astonishing evidence for evolution was a revelation to me. I was aware that humans and chimpanzees share 98 percent of their DNA. That is striking enough, but it becomes far more compelling when one compares the similarities in the genomes of several different species of animals that are not closely related.

Currently, scientists have devised a family tree of more than 3,000 species of organisms, including plants, animals, and bacteria. The family tree comes not from fossil evidence, as was the case with the trees of life I became familiar with when I was taking science in high school and college. Those were based primarily on fossil evidence. They are still quite accurate, given that fossils do exist and do provide striking evidence of ancestry. But the family tree Dawkins describes is based on DNA sequences. And it is far more precise.

Creationists are fond of pointing out how statistically unlikely it would be for evolution to take place purely by chance. “It would be like throwing pieces of a watch in a box, shaking it, and having the pieces accidently assemble into a watch,” I’ve heard it said. Of course those who say this have no clue about how evolution works. It is not driven by pure chance, but by selection pressures - natural selection.

But the family tree of life created by DNA evidence can provide some real statistics. The statistics show that the similarities in DNA sequences among multiple species have to be because the species share a common ancestry. Any other explanation would be so extremely unlikely as to be non-existent. In other words, DNA has statistically proven evolution.

But what if you just don’t believe in statistics? That might only be true because they tell you something you don’t want to know. Nevertheless, DNA is not the only form of evidence for evolution other than fossils. Darwin himself realized that the fossil record was incomplete. Although we have vastly more fossil evidence today than Darwin did, it will never be complete. Fossilization is just too rare an event for that to happen.

But we still have what Darwin had. We have comparative anatomy. Things such as homologous structures and convergent anatomy exist only because species have evolved. It is well beyond the scope of this blog to explain the evidence in detail. Books such as the one by Dawkins do a great job providing all the evidence anyone should ever need.

Suffice it to say that evolution of species through natural selection is now a proven fact. Sure it is still a theory, but only because, like all scientific theories, there is room for improvement in the details. Einstein’s theory of gravity is still a theory, yet we take advantage of it daily when we use our GPS devices. Rocket scientists used its predictions to place satellites in precise orbits. And the theory of evolution has been used extensively to make real-world predictions in medical science, genetics, and paleontology, to name a few.

Researchers in Switzerland have even managed to simulate natural selection using robots. The robots "evolved" over several generations to do their jobs better, to cooperate with each other more, and even to behave civilly toward each other. Researchers programmed the robots to produce random changes in their neural nets, which led to various behavior changes over time. Only the changes that improved performance were kept, just as in natural selection.

There really is no room for any doubt. The fact that 44 percent of Americans doubt evolution is due to the vocal minority of evangelical truth deniers who care nothing of evidence. They have convinced those who were capable of being convinced. Those who have been convinced of creationism are obviously open-minded. It is they who really should read Dawkins’ book or others like it so that they can be exposed to the truth, along with the evidence to back it up. That is something the truth-denying creationists can never provide.

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