The fact that all of life on Earth evolved from a common ancestor is an established certainty. No serious scientist doubts it, but a few politically influential Discovery Institute ‘scientists’ are still promoting discredited Creationism/Creation Science claptrap under the new, ridiculous pretense “Intelligent Design" (see the rediculous ‘documentary’ starring Ben Stein, Expelled). Even as late as 2009 (150 years since Darwin published On the Origin of Species) the Texas Board of Education was still debating over pro-creationism language in state science standards. About 40% of Americans, according to the data cited in Richard Dawkins’s latest book, agree with the creationist members on the Texas Education Board: evolution is false and the events in the Bible are literally true.
While some Americans accept evolutionary biology, the theory’s real power is not in the number of people who comprehend its veracity; it is in the strength of its evidence. Data from every scientific discipline—geology, biology, chemistry, physics, etc.—confirm this fundamental truth: life evolved from simple beginnings, over billions of years, into all of the species alive today—indeed, all of the species that have ever lived on the planet.
In The Greatest Show on Earth: The Evidence for Evolution, the great science expositor lays down a mere scintilla of the data that proves that life evolves by Darwinian principles, without any guiding intelligence: It’s all just mutation, replication, natural selection and time. Dawkins likens his examples to clues in a crime investigation, all of which point to evolution by natural selection as the culprit in the great whodunnit. He lucidly demonstrates how the fossil record, the analogous evolutionary results of selective breeding by humans, experiments, etc., all point to assumptions made by Darwin’s hypothesis. Taken together these data comprise Evolutionary Theory, and, consequently, all of modern biology (see Dobzhansky).
Just like any scientifc theory, evolution is falsifiable: It could, in principle, be shown to be false. For example, the great biologist J. B. S. Haldane observed that a single fossilized rabbit in the pre-Cambrian layer would negate evolution all by itselft. Unfortunately for creationists, all of the fossils are in the layers we would expect to find them if evolution is true.
In fact, every observation and every experiment show that evolution is the mechanism of life. Dawkins points out, all living creatures are geographically distributed as they would be if evolution is a fact: If the flood story in Genesis is true, as 40% of Americans claim to believe, ‘[why] would all those marsupials, but no placentals at all, have migrated en masse from Mount Ararat to Australia? Which route did they take? And why did not a single member of their stragling caravan pause on the way, and settle—in India, perhaps, or China, or some haven along the Great Silk Road?’
The geographic distribution is undeniably supportive, but why can't we see evolution from one species to another take place "before our very eyes"? Well, because evolution takes so long (over tens-of-thousands, millions, billions of years . . .), and because the creatures we are used to seeing have long gestation periods, it is difficult to "see" evolution happening. However, it is not impossible. Among the experiments that Dawkins describes so concisely is the brilliant experiment that the Lenski team did on bacteria (because Bacteria replicate so quickly). This experiment shows speciation happening. Don't believe it? All you have to do is read. It starts on page 117.
The best parts of the book are Dawkins’s discussion of the word Theory and his elucidation of the molecular genetic evidence for evolution; if one merely understands what Theory is in scientific terms and if one grasps the power of comparative DNA studies, then one can only conclude that Darwinian evolution is a fact. Molecular evidence, just one of the facets comprising the Theory, is the most compelling evidence that all life is all part of a pedigree. Darwin died not knowing how individuals passed on their traits to their offspring; he never knew his contemporary Mendel had discovered genetics. If only he had lived to see that riddle solved ... Dawkins imagines that Darwin would be enthralled by the latest expansion of the discoveries of Mendel, Watson, Crick and others, evidence which proves beyond doubt that all creatures belong to a dense, branching family tree. The genome for humans, our entire DNA code, has been sequenced. And it has been compared to all of the great apes. When graphed, the differences reveal a tree pattern, the same pattern that Darwin originally suspected and that modern taxonomy later revealed. Now we know it all the more clearly. As researchers decode the genomes for more and more creatures and plants, we will be able to see more and more how life is undeniably related (see Tree of Life).
Evolution is a fact, and it takes no dogma, no faith, and no suspension of disbelief to understand this. If the 40% who don’t accept this fact of biology would read The Greatest Show on Earth—or any other book on biology for that matter—it’s hard to believe that at least some of them would not come away convinced by the truth. However, it is not hard to believe, alas, that many of them either cannot read or are just too indoctrinated to be convinced of anything inimical to their worldviews, no matter how strong the evidence is.
by Richard Dawkins
Free Press, 2009