they give him a shell ,four goats ,six tomatoes and eleven chickens. before the invention of coins and paper currency ,people used such things for buying and selling . this exchange of goods and services for other goods and services is called barter .around 9000 BC people paid for goods with animals like cows , sheep and camels. some societies used vegetables and plants ,too. then in 1200 BC people in China started using shells as money - mainly cowrie shell. Soon other countries begen to do the same .