Darwin’s sense of the wonder of nature, so clear in this introduction, continues as a theme throughout the Origin of Species. Nature allows each species to reach a high degree of adaptability in its specific environment, as is shown by the formation of a woodpecker’s beak to catch insects, or the structure of a parasite to attach itself to other animals. Natural theologians, or those who believed that God created all species, opposed Darwin’s theory and used his examples of perfect adaptability as evidence of the miracle of God’s creation. Darwin, however, saw nature itself as the miracle, and believed that the natural world deserved our utmost admiration. Darwin’s respect for the power of nature is fundamental to his theory of natural selection. According to his theory, nature controls the selection of the advantageous characteristics that lead to species’ perfect adaptation to their environment.