James Hutton (1726-1797)
…those organized bodies, which most approach to the best constitution for the present circumstances, will be best adapted to continue, in preserving themselves and multiplying the individuals of their race. (An Investigation of the Principles of Knowledge)
James Hutton is best known for his important contributions to the science of geology (uniformitarianism and the great age of the earth). However, Hutton was also the first person to propose a mechanism of natural selection to account for evolutionary change over time. In his book, Investigation of the Principles of Knowledge (1794), he lays out a clear argument for a process of transmutation by natural selection, and does so through analogy with the process of artificial selection (click here to link to the relevant passages). Hutton argues that members of species vary, and that when the environment changes over time, those individuals best adapted to the new environment will survive, while those poorly adapted will perish. Thus, a process of natural selection (Hutton did not use this term) inevitably leads to change within species over time.