Cultural geography is a subfield within human geography. Though the first traces of the study of different nations and cultures on Earth can be dated back to ancient geographers such as Ptolemy or Strabo, cultural geography as academic study firstly emerged as an alternative to the environmental determinist theories of the early 20th century, which had believed that people and societies are controlled by the environment in which they develop. Rather than studying pre-determined regions based upon environmental classifications, cultural geography became interested in cultural landscapes. This was led by the "father of cultural geography" Carl O. Sauer of the University of California, Berkeley. As a result, cultural geography was long dominated by American writers.