On the origins of African slavery in the Chesapeake: At first, much of the agricultural labor in the Chesapeake region, was performed by white bondsmen. A bondsman was bound to a planter for a fixed number of years, say five or seven, to repay his passage to America. Some of them had chosen to come to America; others of them had been kidnapped and brought to America. The bondsmen were both men and women. The planter would buy them from the ship-captain, then they had to work for him for a few years. When their bond period was up, they were free. Severity was often used to maximize the work extracted from them because their master knew that they would be leaving him and he did not care so much about their health and well-being as he might have if they had been permanent workers for him. Because of the severity, the bondsmen often ran away. They went beyond the frontier of settlement and built a hut and planted some food crops. They were white just like every other farmer on the frontier, so it was hard for their masters to detect and recover them.
Blacks, on the other hand, were easy to differentiate and therefore more likely to be recovered if they ran away. Hence, planters started acquiring African slaves. There may have been other reasons; maybe planters could not get enough white bondsmen to do all the work on the plantations.
I have read that the first blacks brought to Virginia were not life-long slaves, but temporary bondsmen just like the whites. I have read that the first black slave in Virginia was owned by a black master. Supposedly, the master had served out his bonded period and become a farmer and had a black bondsman working for him who was simple-minded or in some other way incapable of careing for himself; at any rate the master convinced a court that this was the case and won a ruling by the court that he could keep the bondsman in permanent life-long bondage for his own well-being.