On Darwinism and Human Nature: Darwinism was perhaps the most important ideology to emerge from the nineteenth century. Marxism was a close second, but Darwinism gave birth to more controversy for social scientists, natural scientists, religious figures, and political leaders alike. For historian Carl Degler, Darwinism consisted of three basic principles: first, that organisms reproduce, second, that each organism differs slightly from another (even in the same species), and third, that all organisms must compete for survival (or else face extinction). Thus, bare-bones Darwinism was really nothing more than observational ecology. And it would take the development of genetics by Augustinian friar Gregor Mendel in the 1860s to substantiate some of Charles Darwin's core claims about natural and sexual selection. Darwin himself was worried after he published On the Origin of Species in 1859 that many of his scientific observations would not be fully accepted in the budding community of academic biology. Yet aside from Darwinism's effects on fields like biology and ecology, it had a major impact on the developing world of cultural anthropology. Early anthropologists such as Franz Boas and Margaret Mead were convinced that human nature was more a product of culture than biology. Thus, they began to view racism, sexism, and even eugenics, as incompatible with Darwinism's core tenets, and likened them more to social constructs such as "society" and "history."