Nature is the agent in Darwin’s theory of descent with modification. It is nature, embodied in the forces that act on the process of natural selection, that determines which species survive and which become extinct. Darwin characterizes nature in several ways, some of which are contradictory. Nature is described at times as wondrous and “good,” creating the “perfect adaptation of species” that allows them to survive in the environments in which they live. In other cases, Darwin offers a more dismal view of nature, characterizing it as the limiting factor in a species’ abilities to survive. The limit on natural resources creates the struggle for existence and brings about the end of species by extinction. In this portrayal, nature is a dark and destructive force. Nature is also seen as haphazard. Sheer luck determines which variations will appear in an individual living in a particular environment. The factors influencing which species survive and which die out ultimately boil down to random acts of nature.
Darwin’s dedication to scientific methodology is apparent in his explication of his theories of natural selection and descent with modification. Darwin credits his experiments and observations with allowing him to develop his theory in the first place. Throughout the text, Darwin also cites experimentation and observation—most notably his research and observations of species from his voyage on the H.M.S. Beagle—as evidence in support of his evolutionary theory. Darwin relies on inductive reasoning, constructing theories that are based on facts gathered from experimentation and observation. By using inductive reasoning, Darwin strengthens his case and arms himself with hard evidence. The Origin of Species illustrates how scientific inquiry provides tools for discovery, knowledge, and truth.
The perfection that many of Darwin’s contemporaries observed in an organism’s suitability for its environment was, to Darwin, only a “seeming perfection.” According to Darwin, natural selection and descent with modification enable the natural world to progress toward a continually more perfected state. As advantageous variations appear and are naturally selected and perpetuated in future populations, a species’ adaptability to its environment becomes increasingly more complex. Over time, species reach new heights of perfection, creating the “wondrously adapted” species seen today. Because of the random, unpredictable nature of variation, Darwin notes, progression is gradual, occurring in incremental steps over a long period of time. The process of natural selection, however, can only create better-adapted species. It never creates species that are worse off than their forebearers were. Darwin’s theory of natural selection presents evolution as an inherently positive progression of the natural world, with each species continually moving toward perfect adaptation.
Nowhere in The Origin of Species does Darwin explicitly mention how humans fit into his theory of evolution. However, at various points in the text he hints that humans evolve just as animals do. In comparing the bone structures of particular organisms, for example, he compares the hand and arm structure of humans with the wings of the bat and the paddle arms of the porpoise. This comparison implies that humans are part of the same evolutionary scheme that created bats and porpoises. Darwin also explicitly states his belief that all organic beings are included in his scheme of descent with modification, a statement that implicitly encompasses humans. Darwin’s hints about humans’ place in the evolutionary scheme have serious implications. By blurring distinctions between humans and animals, Darwin throws into question the uniqueness of human beings in the natural world. He implies that nature, not God, controls human development. And he puts forth the question of whether humans should conceive of their societies in terms of Darwinian ideas about progress, struggle, and natural selection.