Final answer:
Nineteenth century evolutionists like Charles Darwin and Alfred Russel Wallace made foundational assumptions about species change and natural selection in the development of evolutionary theory. Alfred Russel Wallace independently arrived at a theory similar to Darwin's, and James Hutton's and Charles Lyell's geological theories also contributed to the evolutionary framework.
Step-by-step explanation:
The nineteenth century evolutionists, notably Charles Darwin and Alfred Russel Wallace, made several foundational assumptions in developing the theory of evolution. These assumptions included the idea that species were not immutable but could change over time, that there was a common descent for all forms of life, and that the mechanism driving these changes was natural selection. An important figure who independently derived a theory of evolution similar to Darwin's was Alfred Russel Wallace. Wallace's work prompted Darwin to publish his ideas more quickly.
Another influential naturalist of the time was James Hutton, whose gradualism theory paved the way for Charles Lyell and subsequently influenced Darwin. Jean-Baptiste Lamarck, although his mechanism for evolution was eventually discredited, also influenced early evolutionary thought. Social Darwinism later applied the principles of natural selection to human society, often justifying imperialism and racism under the pretext of biological differences.