Today marks the 205th birthday of the late Charles Darwin. Although the great scientist is extinct, the theory of evolution—that all organisms are descended from a single, common ancestor—is more alive than ever. Darwin published his theory in the Origin of Species more than 150 years ago. Since then, the theory of evolution has been confirmed to a remarkable degree. As the late Russian Orthodox Christian Theodosius Dobzhansky wrote, “Nothing in biology makes sense except in light of evolution.” Yet despite more than 150 of evolutionary progress, many Americans still deny evolution as a scientific fact. Too often, high-school students are referred to pictures of peppered moths as examples of evolution. Yet there is a plethora of exciting discoveries that confirm evolutionary theory which far exceed examples of peppered moths. So sit back, dear reader, as we travel down high-school biology memory lane for an updated lecture on evolutionary theory.
If there is one nail in the coffin that substantiates evolutionary theory, it is genetics. Just as scientists can appeal to DNA to determine whether person A is biologically related to person B, scientists can determine whether organisms are related to each other by using modern-day DNA techniques. Through modern DNA techniques, scientists can compare the pattern of resemblances between the genes of any two animals. In particular, scientists compare the letter to letter correspondences between the genes. This even works with pseudo genes, which are genes that no longer function. When the pattern of resemblances is plotted out, it forms a beautiful hierarchy. The only way to make sense of this hierarchy is that it is a family tree.
In addition to the plotting out genes, this hierarchy is cross confirmed by phylogeny and Linnaean taxonomy. Phylogeny is the method of categorizing organisms based upon their DNA, whereas Linnaean taxonomy is a method of classifying animals based upon their morphology. For example, if person A shares more than fifty-percent of their genes with person B, then person B is person A’s mother or father. This method is so reliable that is constitutes legal proof in a court of law. As referenced earlier, this method can and has been used to determine whether all organisms are related. In addition, the family tree plotted by phylogeny is cross-confirmed by the family tree developed by Linnaean taxonomy, which classifies organisms according to their morphological features rather than their DNA. So in this instance, we have two fields of biology using separate methods that cross-confirm each other!
If that were not enough to convince someone of evolution, there is more. It is widely known that humans have 23 chromosome pairs. Evolution predicts that we share a common ancestor with the apes, chimpanzees, gorillas and orangutans. Yet apes, chimpanzees, gorillas and orangutans have 24 chromosome pairs, where we only have 23 chromosome pairs. So, where did the extra pair of chromosomes go? Losing an entire chromosome pair would be lethal to the species. Therefore, biologists predicted that the pair of chromosomes must have been fused together somewhere in the past. So we should be able to scan the human genome and find two chromosome pairs that are fused together. If we don’t, evolution is in trouble. It turns out that it is our chromosome number two. Our chromosome number two was formed by the fusion of two primate chromosome. In short: it’s there, it’s testable and it confirms the prediction made by evolutionary theory.
Yet the explanatory power of evolutionary theory is not bound to biology. What makes evolutionary theory so powerful is its ability to makes sense of a wide range of observations found in other scientific disciplines. The evidence found in paleontology and the geographical distribution of animals has not even been scratched. It is often argued that no amount of evidence will convince a creationist out of their beliefs. Although this may be true for a few radicals, this claim is demonstrably false. This author is living proof of this statement. Nevertheless, details regarding evolution continue to occupy biologists, such as the primary mechanism under which evolution operates. Although the fact of evolution remains, the theory of evolution is still evolving.
By Nathan Cranford