Slavery has taken place from the beginning of man kind; the enslavement of the mankind has been found in the Ancient Mediterranean civilisations, such as Greece, Egypt, the Akkadian Empire and the Roman Empire. The Vikings in c.793AD captured and enslaved their opponents from Western Europe.
There was also a trade in serfs in England, but this was made illegal whilst the trade in Africans remained legal until 1807. Slavery has also existed for centuries in Arabia, the Ottoman Empire and the Middle East. The Arab Slave trade was one of the oldest, predating the European Transatlantic Slave trade by a few hundred years. They Arab traders were able to buy slaves from the African slave markets, which existed inland and showed that slavery existed there before the European Transatlantic Slave Trade.
The European Slave trade was begun by the Portuguese, who began the trade in Africa as a means of evangelism. They hoped to convert the ‘heathens’ but soon it become profit based. This trade began about in the 1400s and was continued until the 1900s by other nations, such as the English, Dutch, Danish, Spanish, Germans and Russians.
It was a matter of the Old World, the European countries, exporting slaves to the New World, the Americas. And although it was outlawed in most countries, slavery still exists today in many of the same forms.
Slavery is a human institution, which is ancient but also flexible, as it will adapt to the prevailing social circumstances. Also it is a great facilitator of social mobility, so it is a system which helps develop new societies. Such an example was the case with the Transatlantic Slave Trade and the economic devices used to buy slaves. It started with bartering but quickly developed into more complex systems of credit and insurance.