from the 6th century at the latest. The considerable amount of daub found indicates timber buildings, and shell beads, bead grinders, and iron slag have been found at the site. There is evidence of limited engagement in long-distance trade: a small amount of imported pottery has been found, less than 1% of total pottery finds, mostly from the Gulf and dated to the 5th to 8th century. The similarity to contemporary sites such as Mkokotoni and Dar es Salaam indicates a unified group of communities that developed into the first center of coastal maritime culture. The coastal towns appear to have been engaged in Indian Ocean and inland African trade at this early period. Trade rapidly increased in importance and quantity beginning in the mid-8th century and by the close of the 10th century Zanzibar was one of the central Swahili trading towns. Excavations at nearby Pemba Island, but especially at Shanga in the Lamu Archipelago, provide the clearest picture of architectural development. Houses were originally built with timber (circa 1050) and later in mud with coral walls (circa 1150). The houses were continually rebuilt with more permanent materials. By the 13th century, houses were built with stone, and bonded with mud, and the 14th century saw the use of lime to bond stone. Only the wealthier patricians would have had stone and lime built houses, the strength of the materials allowing for flat roofs, while the majority of the population lived in single-story thatched houses similar to those from the 11th and 12th centuries. According to John Middleton and Mark Horton, the architectural style of these stone houses have no Arab or Persian elements, and should be viewed as an entirely indigenous development of local vernacular architecture. While much of Zanzibar Town's architecture was rebuilt during Omani rule, nearby sites elucidate the general development of Swahili, and Zanzibari, architecture before the 15th century. From the 9th century, Swahili merchants on Zanzibar operated as brokers for long-distance traders from both the hinterland and Indian Ocean world. Persian, Indian, and Arab traders frequented Zanzibar to acquire East African goods like gold, ivory, and ambergris and then shipped them overseas to Asia. Similarly, caravan traders from the African Great Lakes and Zambezian Region came to the coast to trade for imported goods, especially Indian cloth. Before the Portuguese arrival, the southern towns of Unguja Ukuu and Kizimkazi and the northern town of