Anthropology is a global discipline where humanities, social, and natural sciences are forced to confront one another. Anthropology builds upon knowledge from natural sciences, including the discoveries about the origin and evolution of Homo sapiens, human physical traits, human behavior, the variations among different groups of humans, how the evolutionary past of Homo sapiens has influenced its social organization and culture, and from social sciences, including the organization of human social and cultural relations, institutions, social conflicts, etc. Early anthropology originated in Classical Greece and Persia and studied and tried to understand observable cultural diversity. As such, anthropology has been central in the development of several new (late 20th century) interdisciplinary fields such as cognitive science, global studies, and various ethnic studies.