ABSTRACT
Charles Darwin argued that organisms come about by evolution, and he provided a scientific explanation, essentially correct but incomplete, of how evolution occurs and why organisms have features—such as wings, eyes, and kidneys—clearly structured to serve specific functions. Natural selection was the fundamental concept in his explanation. Genetics, a science born in the twentieth century, revealed in detail how natural selection works and led to the development of the modern theory of evolution. Since the 1960s, a related scientific discipline, molecular biology, has enormously advanced knowledge of biological evolution and has made it possible to investigate detailed problems that seemed completely out of reach a few years earlier. We have learned, for example, how similar the genes of humans, chimpanzees, and gorillas are: they differ in about 2 percent of their DNA.
