Are yams and sweet potatoes the same?
specialized form of barter in which goods are exchanged without any direct contact between the traders. Generally, one group goes to a customary spot, deposits the goods to be traded, and withdraws, sometimes giving a signal such as a call or a gong stroke. Another group then comes to leave a second set of articles and retreats. The first group returns, removing these new goods if satisfied or leaving them until additions are made. The second group then takes the original wares to conclude the transaction