Commerce

The new diet of settled farmers - predominantly vegetarian, with meat now an occasional luxury - results in one small but significant development. Salt becomes an important commodity in human trade.

A physical necessity of human life, salt exists in sufficient quantity in a diet of milk and of raw or roasted meat. It is not present in vegetables, grain or boiled meat. Agriculture in many areas of the world (freshwater districts without mineral deposits of sodium chloride) only becomes possible if a trade in salt is established. As a result salt features in many of the most important trading systems of the world. The caravan routes crossing the Sahara are a prime example.

Sources

http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ab63#ixzz3BCv9DYMf