Why did English settlers turn to Africans for slaves?

Slavery existed in the American colonies almost from their inception. A Dutch ship brought the first slaves to Jamestown in 1619.
European settlers used slaves because they were a cheap labor force. In Spanish America, Indians were enslaved, but their high mortality rate led to the use of African slaves. By the late 17th century, slavery was an important characteristic of British America.
Many immigrants who arrived in America were indentured servants. Indentured servants had to work for five years to pay off the cost of their voyage to the New World. They were given room and board, and perhaps some land when their service ended. But settlers came to prefer the use of black slaves; they were able to keep slaves in perpetuity and slaves had no rights.
Slaves were used primarily on agricultural plantations. Small farmers could not compete effectively against agricultural plantations which had large numbers of slaves. An increasingly efficient slave trade provided an endless supply of labor. The South's agricultural economy was eventually based on slavery.
Today, the practice of slavery is widely abhorred. But the use of slaves in colonial America was not surprising, because slavery dated back to ancient Greece. When viewed in its historical context, its development in the colonies was almost inevitable.