Although the Alps did not mark political boundaries, they often separated groups of people from one another. Because in the past the Alps were impassable, inhabitants isolated in valleys or networks of valleys developed distinct regional subcultures. Consequently, the inhabitants of one valley frequently maintained dialects, native or traditional dress, architectural styles, and folklore that substantially differed from those of the next valley. Differences were great enough that the origins of outsiders could easily be identified. However, mass media, mobility, prosperity, and tourism have eroded the distinctness of Alpine regional subcultures to a great extent by reducing the isolation that gave them their particular character.