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 countries began to do the same. The cowrie shell was very successful. It was used longer and in more places than any other currency in history.