Charles Darwin was born 206 years ago this month, and each February we reflect on his theory of evolution by natural selection — the central idea about which the biological sciences revolve.
Yet, sadly, despite overwhelming evidence supporting the model, more than a third of Americans still doubt the reality of evolution. Time and again, the same objections are raised. But these criticisms can be shown to be fallacious, based on a flawed understanding of the subject.
Here’s my attempt to address a few of the more common misconceptions:
Macro-evolution has never been observed: Biologists define evolution as a change in the gene pool of a population over time. Only rapidly reproducing organisms can be observed in the act of such a change. An example might be microbes developing a resistance to antibiotics, or insects becoming pesticide-proof. Even most creationists recognize that evolution at this level is a fact — they call it “micro-evolution.” This is a red herring, however, for macro-evolution is just the sum of these micro-evolutionary changes over a long span of time. Furthermore, evidence isn’t limited to seeing changes occur before our eyes. One need only consider the fossil record, comparative anatomy, genetic sequences and geographical distributions of species. The number of observations supporting “macro-evolution” is overwhelming.
Why are there no transitional fossils? Though the fossil record is spotty, as conditions have to be just right for fossilization to occur at all, we nevertheless have found many instances of intermediary organisms. Tiktaalik — a transition between fish and amphibian, Ambulocetus — between a land mammal and the modern whale, and Archaeopteryx — a creature bearing the characteristics of both reptiles and birds are but a few examples of transitional forms. The evolution of the horse is also well-documented with a wealth of transitional fossils.
The complexity of life couldn’t occur by random chance: While chance mutations certainly play a role, there is nothing random about natural selection. The constant culling of the less well-adapted (or less mate-attractive) from the gene pool is a rather severe filtering mechanism, the very opposite of chance.
If man came from chimps, why are there still chimps? This is akin to asking, “If we came from our parents, why do we still have living cousins?” Humans did not descend from modern chimps. Rather, we share a common ancestor. The stumbling block here is the mistaken idea that evolution occurs in a straight line, where entire populations change into new species at the same time, as though on a ladder of ascent. A better analogy is a continually branching tree. Evolutionary theory never states a source population must go extinct in order for a new species to evolve.
Information cannot be created by genetic mutation: Mutations can occur during the copying of DNA, and these can take the form of additions, deletions or changes to the genetic code, or duplication of entire sections or genes. Color vision is a great example of this. While most mammals have two types of retinal cones, corresponding to red-green color blindness, most primates, including humans, have three types of cones. The study of the DNA reveals that the evolution of primate color vision was due to a gene duplication coding for one of the kinds of cones. Information is created, and that small difference in the gene allows primates to distinguish red from green, conferring an obvious selective advantage.
Evolution is only a theory, it hasn’t been proven: The misunderstanding here lies in the definition of “theory” itself. Unfortunately, in common usage the term theory can mean hypothesis or best guess; however, evolution is a scientific theory — an explanatory model which makes testable predictions and has been substantiated with corroborating evidence. The theory of evolution has been supported with vast amounts of incontrovertible evidence, and no better explanatory model has ever come along.
A good theory makes both verifiable and falsifiable predictions about the natural world, and Darwin clearly demonstrated this. When he saw that the Star Orchids of Madagascar have 11½-inch nectaries, with the bottom 1½ inches filled with nectar, Darwin expected that, like all other smaller orchids of this variety, a moth would be required to pollinate it. Not just any moth, but a very large one with a never before seen 10-inch proboscis to extract the pollinia floating within the nectar. Decades later, the giant moth Xanthopan morgani praedicta was found and documented with a 10-inch snout, confirming the prediction.
Evolution also predicts a relatively well-ordered fossil record, with earlier organisms located in deeper strata of the rock. This is exactly what is found, rather than the haphazard record you’d expect if fossils were strewn about all at once in a worldwide flood. In other words, if rabbit bones were ever found in Precambrian strata, evolution would be falsified. This hasn’t happened.
Darwin arrived at the truth of evolution by natural selection without the benefit of the science of genetics, and for that he deserves credit.