Given limited evidence from around the world, houses were probably used at much earlier periods as well, but will be hard to find. Increasing use of houses with expanding population densities and technologies relating to storage mark this period. Shell middens appear all along the coast as groups took advantage of the expansion of shellfish into rocky habitat created by stabilized and modern sea levels. This period also marks increasing regionalism in styles associated with the manufacture of artifacts and in art or religious objects. There are the clear beginnings of a NW style, a Plateau style, a Basin style and styles associated with the California region.
Trade networks become more complex.
Many more localized tool-rock sources are exploited, and trade increases in its distances and in scope. The beginnings of the Columbia River trade network are developed as a natural outgrowth of the river system and its intrusion through many different ecological regions deep into the continental interior. Kathryn Toepel excavated the Flanagan Site as part of a University of Oregon field school in the 1970's. The site contained both Middle and Late Archaic occupations. The projectile points for this period are dart points with wide necks.