People were able to specialize in what they did well, produce more than they needed and trade the surplus to obtain the other goods and services they needed. Individual abilities differ so specialization allows people to produce what they are best at. In economics this is explained by the theory of comparative advantage. A person who concentrates on one activity tends to get very good at it over time. This is typically referred to as learning by doing .
Specialization only works if there is trade.
Early trade took place as mutually agreed upon exchanges between neighbors and over time moved to local markets. Early trade took the form of barter exchange of goods and service for other goods and services. The efficiency of trading increased enormously with the advent of money. These advances made possible what economists refer to as the division of labor specialization of labor within the production process of a single good or service. The division of labor involves dividing labor into a series of repetitive tasks where each person performs a single task, which is only one of many necessary to produce a good or service.