But let’s be clear: This is not evolution versus God. The existence of God—any sort of god, personal or abstract, immanent or distant—is not what Darwin’s evolutionary theory challenges.  What it challenges is the challenge of the supposed godliness of Man—the conviction that we above all other life forms are spiritually elevated, divinely favored, possessed of an immaterial and immortal essence, such that we have special prospects for eternity, special status in the expectations of God, special rights and responsibilities on Earth. That’s where Darwin runs afoul of Christianity, Judaism, Islam, and probably most other religions on the planet.

—David Quammen, The Reluctant Mr. Darwin, pp.208-209

As I was growing up I believed that God had created the world. Not in the six days and in the order of Genesis, but that the world existed because of God. I know that I did not believe that the world had been created exactly as Genesis described (either of the two chapters, Genesis 1 or Genesis 2, they’re not the same). The Bible was a book, the stories in it were like Aesop’s Fables, B’rer Rabbit stories, the Grimm’s Fairy Tales, stories, legends, myths, made by Man to tell a story to illustrate a point, a moral, or just for fun.

It was a surprise to me in 10th grade history when Jesus was presented as an actual, an historical person. It was also in the 10th grade biology class though that evolution was presented to me. I first thought that evolution was a metaphor to help explain and understand the biological world. If we looked at animals as if they had evolved from simple one-celled organisms into vertebrates, amphibians, reptiles to mammals we could gain a better understanding of biology. That scientists meant that simple one-celled organisms had actually evolved, that there was a direct, physical, genetic relationship between species was surprising when I realized it. That evolution was not a “metaphor,” that it was meant to have really happened.

Evolution, or as Darwin called it “descent with modification,” is true. It can be seen, measured, and described. Populations of organisms reproduce and change. This change is not necessarily observable, physical change, but a change in the frequency of the genes in the population’s gene pool. The change may result in an observable difference in the physical characteristics of the individuals in the population.

You can look around yourself at all the different breeds of dogs, cats, horses, cows, pigs, chickens, sheep, goats, and the varieties of apples, pears, corn, tomatoes, potatoes, peas, etc. to see the changes between these domesticated species and their wild ancestors, or just between the breeds and varieties of the same species. These examples, you may argue, are examples of human-caused evolution— artificial selection— and not evidence of evolution. I think you are wrong that this matters. It is still descent with modification. Man has only sped up the rate of change and controlled its direction. However, natural examples are the new strains of influenza, antibiotic resistant “germs,” pesticide-resistant insects (man many have deliberately introduced antibiotics and pesticides, but he did not knowingly or willing select for resistant forms, that was a natural result).

The Grants, Peter and Rosemary, have spent years with their research teams, studying several species of finches on an island in the Galápagos archipelago (see Jonathan Weiner’s 1994 The Beak of the Finch). By measuring the length, width, and depth of the beaks of the finches living on the one island, knowing who survived and who bred, and correlating that data with the data on seed production and climate (rainfall mostly) they demonstrated that the size of the beaks changed from year-to-year, the evolution of beak size. The size changed in response to the climate’s effect on the seed crop (size, hardness, number), beak size tracked the climate change. Not only did the population of finches evolve (genetic traits changed from one generation to the next), but the traits changed in a predictable way in response to some external factor. Not only did this research demonstrate evolution but it also demonstrated evolution by natural selection.

Jonathan Wells (in his Icons of Evolution) points out that the beak size oscillated back-and-forth, from smaller to larger and back to smaller. He claims that this doesn’t show evolution at all, apparently because there was not a net change in a direction. He can claim it, however that doesn’t mean he is right. The trait (beak size) does oscillate back-and-forth. The climate oscillated between arid and drought. It did not change in one direction and stay there. Beak size did evolve, evolution does not mean that the change has to be in one direction and has to stay there. Evolution only requires that there be a change from one generation to another (actually a change in the population over some period of time).

The word “evolution” gets used in three different ways. The first way—change in gene frequency of a population over time—is true as discussed above. The second way, as in “the evolution of the horse,” is about the historical pathway that the evolution of a particular species took, its “phylogeny.” That species evolved in a particular way, Equus from Hyracotherium, birds from a theropod dinosaur or from an earlier reptile, may still be open to discussion and not certainly known. The third use of the term evolution refers to its cause. Although Creationists and others may use “Darwinism” as a synonym for evolution and may believe that Darwin invented evolution, the words are not synonyms. The idea of evolution was around long before Darwin (well Charles anyway, his grandfather Erasmus might have a better claim to inventing evolution). Darwin’s contribution was for postulating a workable cause for evolution—natural selection. By proposing a workable cause Charles Darwin made evolution (the first meaning) scientifically respectable.

Others have postulated other causes of evolution—saltationism, random walk, elan vital, punctuated equilibrium, to name a few. Evolution by natural selection may be shown to be not true, or more likely not the whole story. This is a separate issue to the reality of evolution. That is why it is possible to say that evolution is a fact, that evolution by natural selection is a hypothesis.

Evolution, inheritable change, is a fact. It has occurred in populations over time. It doesn’t matter whether you believe it or don’t, change happens. Evolution happens.