The image most associated with the evolution of humans is the procession of primates called the Scala Naturae, and it is also very misleading. It suggests that evolution is a ladder, when it is actually a tree; that we are superior to the other animals, when we are not. This graphic is not much better, but it is closer to the way evolution should be understood (from Wikimedia Commons).

Evolution is the scientific explanation of the formation of the diversity of life on this planet, through the evolution of simple life forms to complex ones over long periods of time, in response to environmental conditions, by means of natural selection: features that develop that are of use in the survival and reproduction of a life form are passed on to further generations. Since the principles of evolution through natural selection were first proposed by British naturalist Charles Darwin some 150 years ago, evolutionary theory has become, through constant research and refinement, a cornerstone of the science of biology. This means that evolution has been an important factor in the development of medicine, agriculture, the environmental sciences and other fields concerning the study of living things.

But evolution has been as controversial among non-scientists as it has been important and useful for scientists. Because it asserts that life forms evolve, it has often been considered to contradict the Biblical account of the creation of the world and of life as given in the book of Genesis. In the United States, there has long been a significant minority of Christian believers who hold that the Bible is the inspired word of God and as such is also literally, factually true, and who therefore believe that the teaching of evolutionary theory is dangerous to religious faith. They have therefore waged war in legislatures, the courts, school boards and the media against the teaching of evolution, making assertions that belie a profound misunderstanding of science. These include:

  • Evolution attempts to disprove the existence of a divine creator. Neither evolution nor any other scientific theory attempts to support or deny the existence of a divine creator, because the scientific method excludes the supernatural and restricts itself only to what can be measured, tested, and verified. No body of theory in any branch of science can be construed to be a statement in favor of the existence or non-existence of God. It is not part of the mission of scientific inquiry to prove or disprove the existence of God. Anyone may, if they wish, interpret the information and concepts of science as evidence of a divine creator, but this is philosophical or theological thinking, not science.
  • Evolution teaches that men came from monkeys. This was an early charge leveled at evolution, and is still heard from critics of evolution who wish to suggest that evolution is absurd or degrading to human dignity. Humans are members of a large class of mammals called primates, which include monkeys, apes, and other creatures. We are related to modern monkeys and apes, but we are not descended from them; rather humans and other primates share a common ancestor. Humans are one branch of the primate family; the monkeys and the great apes are two others. Whatever conclusions individuals may come to from this fact about the dignity or divine heritage of human beings is, like the existence of God, not the concern of scientific inquiry.
  • Evolution is “only” a theory and has not been proven. This confuses the scientific understanding of the word “theory” with its popular, colloquial understanding as a guess or hunch. A theory is only referred to as such in science when it has been tested and shown to be consistent with all the evidence and to accurately predict outcomes. Over 150 years, scientific research has repeatedly proven the accuracy of the evolutionary explanation.
  • Evolution is “controversial” within the scientific community. There is plenty of controversy in our culture about evolution, but not in the scientific community, where the principles of evolution are overwhelmingly accepted. Science is not a democracy where different “parties” battle for dominance. When evidence is presented, concerned scientists study that evidence, review the methodology, and if sound, accept it. By the same token, astrophysicists accept that the earth revolves around the sun, because the overwhelming body of evidence proves that this is indeed the case, as opposed to the sun revolving around the earth, for which there is no evidence.
  • There are “gaps” in the theory of evolution which argue against its acceptance. There are gaps and unknown facts in every branch of science, but they do not argue against the credibility of what is already known. Nor do gaps and unexplained facts argue for the intervention of a divine being: this is known as an “argument from ignorance” and implies that if we cannot explain something, then the explanation must have something to do with God. In fact, it only means that we do not understand something yet, and probably will be able to understand it at some time in the future, as with every other discovery made in the history of scientific inquiry.
  • There are phenomena in the natural world which are too complex to have evolved simply by chance. This is the “irreducible complexity” argument, used by advocates for “intelligent design”, and most of the examples they use are simply misunderstandings of already known facts. First off, evolution does not work by “chance”, but by a cumulative process of change made up of smaller changes over time. Random mutations appear in the structures of organisms which may or may not be useful in survival and reproduction. Those that do provide a benefit end up transmitted to later generations, building up to greater and greater differences in structure. We can study these structures and find indications of earlier structures and the way they changed, for instance, the limbic system in the human brain, which is a legacy of the reptilian brain, or the “hammer and anvil” in the inner ear, which descends from the multiple-boned lower jaws of early vertebrates, or the human eye, in which we can trace the evolution of animal vision from spots which simply registered light and dark, to the camera-like eyes of later animals which could actually register images, in progressively greater detail, sharpness, and richness. All these examples show, not an overall sense of design, but changes building on already-existing structures, like rooms added onto a house; and we can also discern flaws in the results that further make the idea that we were “intelligently designed” unlikely. Richard Dawkins points out in his book The God Delusion that many human ailments like hernias, prolapsed uteruses, sinus infections and back pain are traceable to our having evolved from animals that walked on all fours to animals that walked on our back legs.
  • No one has ever observed evolution happen. Evolution is a historical science in which many lines of inquiry converge: biology, zoology, molecular biology, developmental biology, geology, genetics, comparative anatomy, paleontology, genome sequencing, embryology, and other sciences. In studying these various fields, scientists find patterns and common features of development between independent sets of data. It is these independent lines of evidence coming together that confirm evolution, not direct observation of change in real time. Although, we can also do that with organisms with very brief reproductive cycles, such as bacteria and viruses: the appearance of strains of diseases such as tuberculosis, influenza, or syphilis that are resistant to existing vaccines or antibiotics is a result of evolution in action.
  • There are “alternative” theories about the origin of biodiversity which have been suppressed by atheistic evolutionists. This argument incorporates several concepts dealt with above: the equation of evolution with atheism, the misunderstanding of what the word theory actually means, and the imputed controversy over evolution which is, as we have seen, not in the scientific community but in the realm of popular culture and politics. These alternative “theories”, variously called “creationism” and “intelligent design”, do not involve published, peer-reviewed research but cherry-picked quibbles over existing, already-verified evidence, most of which have been adequately answered by evolutionary scientists.
  • Advocates of creationism/intelligent design are simply arguing for academic freedom and open inquiry. If the assertions of creationism/ID advocates were actually doing work that had demonstrable scientific merit, this might be true. But the first requirement of science education is that what is taught actually be science. If something does not have scientific merit, it does not belong in a science classroom. “Teach the controversy” is also a common catch-phrase among advocates of creationism/ID, but as stated, this controversy is not a scientific one, but a cultural and political one. In fact, creationism and ID are not scientific theories, but religious advocacy masquerading as science, as has been demonstrated repeatedly in America’s courts, and as such does not belong in a science classroom.

The theory of evolution is the product of honest inquiry following a rigorous method and leading wherever the evidence points, and is one of the greatest revolutions in the history of human thought. This inquiry was not done with the purpose of upsetting people or endangering religious faith. If a scientific theory in fact does endanger the faith of some (and no less an authority than Pope John Paul II has said that acceptance of evolution is in no way incompatible with Christian faith), that is not a problem of the theory, but of the nature of one’s faith.

It’s legitimate to have differing interpretations of facts, provided that there is agreement about what those facts are. The scientific method works because it offers a framework for the correction of errors and thus excludes from the discussion any possible disagreement about the evidence: the earth does revolve around the sun and simple life forms do evolve into complex ones over time by means of natural selection. Until such time that the scientific community concludes, on the basis of verifiable and peer-reviewed research, that evolution through natural selection is not the way Earth’s biodiversity came into being, one may not come up with one’s own set of facts and teach them as science.