Sociocultural anthropology has been heavily influenced by structuralist and postmodern theories, as well as a shift toward the analysis of modern societies. During the 1970s and 1990s, there was an epistemological shift away from the positivist traditions that had largely informed the discipline.[page needed] During this shift, enduring questions about the nature and production of knowledge came to occupy a central place in cultural and social anthropology. In contrast, archaeology and biological anthropology remained largely positivist. Due to this difference in epistemology, the four sub-fields of anthropology have lacked cohesion over the last several decades.