Stefan Molyneux claims in The Truth About The Crusades that:
Islam dominated slave trade between the 7th and the 15th century, while the Christians entered the market of human flesh much later - 1519 to 1815 is the period of Christian slave trading.
He also claims in The Truth about Slavery: Past, Present and Future that:
Slavery was indigenous to African and Arab countries before it made its way to Europe.
Did Islam dominate slave trade, and did Christians enter the slave market about only later?