Ecology is the study of the interactions between organisms and their environment. The field was established in 1858 and further developed by the contributions of Darwin and Wallace. Julian Steward coined the term "cultural ecology" in 1955 to describe his methodology for examining the relationships between human groups, their environment, and how ecological factors influence aspects of culture like subsistence and technology. Steward also proposed the theory of "multilinear evolution" to explain that cultural change occurs through different processes in different areas, rather than universally or in one direction. He conducted studies applying these ideas to Native American groups and others.