I think that the Marxist notion of dialectical materialism is rooted in the same form of reason as Darwin's idea of natural selection. Both stress the idea that human existence is underscored by some other element. The development of reason in terms of how humans behave is guided through another force. For Darwin, it is survival through natural selection and evolutionary scope and sequence. For Marx, dialectical materialism is what underscores human reason. It is through economic materialism and the organization of social orders based on economics that drives the basis of human reason. In both Marx and Darwinian thought, it is another element of social construction that guides human reason and the formulation of thought. In both sets of thought, human reason cannot escape some other force of being. Being true Modernists, Marx and Darwin see another element that helps to guide and control human reason. Darwin views this through the lens of evolution and survival of organisms. Marx sees this element of reason through the social organization offered by dialectical materialism.