Evolution is a scientific theory holding that biological species can change through time into different ones. Through the years evolution has often been referred to as decent of species with modification. As part-and-parcel of this view of life, living organisms are thought to share genetic continuity with one another and with species that lived in the past. All life on earth is believed to share common ancestry. From its beginnings, an evolutionary views of the history of life engendered considerable controversy on a variety of levels. The reason for this is evolution replaced very ancient ideas holding that species are static entities, incapable of substantial change. Static views of nature had important scientific, ideological, religious, and political meaning and evolution was part of the challenges to them. Clearly, no other scientific theory is as ideologically linked as evolution, has been co-opted for so many various and often contradictory political purposes, or has as much to say about whom and what we are. In addition, evolution played an important role in transforming biology and natural history into modern science by unifying the many disparate areas of study which were part of these disciplines under a common intellectual paradigm. In doing so, evolution freed biology from theological constraints. This work attempts to place twenty-first century evolution into an historical and ideological context. New ideas and discoveries that have shaped, and are shaping, evolution are discussed within this framework. As an outcome of this endeavor, the development of evolutionary theory is used as a model for exploring how scientific ideas emerge and for exploring the nature of science.
