Slaves often served as a form of wealth in primitive societies, making slaves a suitable medium of exchange, particularly for large transactions.
In the modern era Africa provides the most evidence of the use of slaves as money. In the nineteenth century a slave was the unit of account in the Sudan. A standard unit was defined as a slave that met certain measurements. The value of a slave was equivalent to 30 cotton pieces, 6 oxen, or 10 dollars. In the Bagirmi country of equatorial Africa a slave of medium qualities, defined as a standard slave, served as a standard of value for large transactions. The prices of better slaves were some multiple of the standard slave. Wealth took the form of “heads,” and a successful slave raid depreciated the value of the standard, causing the prices of commodities expressed in slaves to rise. In Ghana slave payments were made for large transactions, and slaves served as a standard of value. In Guinea slaves were the favored unit of account in large transactions, and kings charged European ships port dues ranging from 7 to 12 slaves, depending upon the number of masts on each ship. In Nigeria slaves ran a close second to cowries as the prime unit of currency. A report in the late nineteenth century said of the slave: “He has been the cheque book of the country and has been necessary for all large payments. Unfortunately he has a trick of dying while passing from hand to hand” (Einzig, 1966).
The standard of value was defined in terms of a slave of a certain age, and in the course of a transaction each slave was valued in terms of this standard slave. In Nigeria, slaves were the choice medium of exchange for large transactions, and rich men amassed wealth in slaves. In the Congo slaves passed in payment for goods, and met the need for a standard of value. The people of this area practiced cannibalism, and the value of a slave could not drop below the value of the pounds of meat that could be gotten from the slave if the owner ate his money. In seventeenth-century Angola a 20-year-old slave was a standard unit of value.
Some authors pin the blame for African slavery on the absence of a convenient currency. Slaves were mobile and often carried other forms of primitive money that was bulky and difficult to transport. Merchants brought slaves carrying other currencies on trading expeditions, and exchanged the slaves along with the other currencies for merchandise when the opportunity arose.
In early Cambodia slaves ranked with cattle, buffaloes, horses, pigs, and elephants as an acceptable means of paying fines. In early England values were occasionally estimated in slaves, and in Ireland a unit of account of one slave girl lasted well into the Christian era, long after the practice of trading human beings for goods had ended. People in western areas of New Guinea priced calico and other traded goods in terms of slaves.
The use of slave money probably began when warriors took more captives in war than they could personally use, and therefore they traded these captives for goods. From this small beginning the practice of trading human beings evolved into the use of slaves as a type of money.
Einzig, Paul. 1966. Primitive Money.
Weatherford, Jack. 1997. The History of Money.