From the beginning of the nineteenth century, Nyamwezi long-distance trading caravans dominated the central routes through Tanzania, stretching from Mrima coast ports such as Bagamoyo and Saadani to Ujiji on Lake Tanganyika. Despite the inroads of Omani Arab and Swahili trading enterprises from the middle of the century, the Nyamwezi maintained a position of strength. In the second half of the nineteenth century, market relations emerged as the dominant form of economic organization along the central routes, although the market for many commodities was clearly fractured by transport difficulties, and non-market relations frequently substituted for weakly developed commercial institutions and tools. Most caravan porters in nineteenth-century Tanzania were free wage workers, and nearly all were clearly migrant or itinerant labourers. The development of a labour market for caravan porters was an early and significant stage in the transition to capitalism, which began in a period of violence and political upheaval. Clearly, this has implications for how scholars should view broader processes of economic transformation prior to the imposition of colonial rule, which cut short a series of significant indigenous innovations.

The argument that porters were mostly wage labourers rests on evidence that their labour was bought and sold according to fluctuating labour market conditions. Market conditions in the second half of the nineteenth century shows a broadly rising demand for porters, a demand that could only be met if caravan operators offered adequate wages and observed the customs established within porter work culture. Thus, market conditions along the central routes contributed to the development of a free wage labour, characterized by a unique labour culture.