It's largely a matter of indifference. They hailed from hierarchical societies which made little pretense to equality and granted superiors considerable power, though certainly not unlimited power, to do what they liked to inferiors. Slavery is another layer on the bottom of that and has some fuzzy boundaries with indentured servitude. Some slaves sold in Virginia seem to have been treated the same as whites under indenture. Over the seventeenth century we see that shift increasingly to people arrived from Africa, albeit often by way of the West Indies, having fewer opportunities and receiving harsher punishment than whites.

For example, John Punch and two white indentured servants ran off together. They were recaptured and sentenced on July 9, 1640. Here's the judgment: (Warning, original includes 17th century spelling.)

Whereas Hugh Gwyn hath by order from this Board Brought back from Maryland three servants formerly run away from the said Gwyn, the court doth therefore order that the said three servants shall receive the punishment of whipping and to have thirty stripes apiece one called Victor, a dutchman, the other a Scotchman called James Gregory shall first serve out their times with their master according to their Indentures, and one whole year apiece after the time of their service is Expired. By their said Indentures in recompense of his Loss sustained by their absence and after that service to their said master is Expired to serve the colony for three whole years apiece, and that the third being a negro named John Punch shall serve his said master or his assigns for the time of his natural Life here or elsewhere.

There's a lot to read in this, but it presumes that Punch would otherwise be free after a time. There's no cause to sentence him to life if he already had a lifetime of slavery ahead of him. The court calls out his race as the sole factor distinguishing him from Victor or Gregory. Records from the Chesapeake in this time aren't always the best, but Punch is a fair candidate for the first out-and-out African slave in Virginia. (There may have been Native American slaves earlier; it's something I've yet to study.)

However, we shouldn't project a 19th or 18th century vision of slavery on the Virginia of 1640 through the lens of Punch's case. There are no explicit laws regulating slavery in the colony at the time, not even on the basic matter that children follow the condition of their mothers. The system is fluid and opportunities for freedom remain open, though they do close as the century goes on. The most famous exception to the emerging rule that to be black is to be enslaved and to be white is to be free (which becomes literally not being enslaved) is the case of Anthony Johnson, who came to Virginia as "Antonio, a negro" and managed to buy his freedom, free his family, and did so well that he earned land grants from the colony for sponsoring the indentures of people coming from England. In the 1650s, he even owns a slave of his own who ran away. Johnson believed that his white neighbors lured the slave off and took them to court. The court sided with him and returned his slave. I wrote more about him here.

Exceptions and oddities like that are largely gone by the turn of the eighteenth century.