Two major trends characterized the development of slavery in seventeenth-century Virginia. The first is that it expanded rapidly as the profitability of tobacco cultivation encouraged planters to put large amounts of capital into labor. The second was that slavery became, as the question states, race-based. This was significant because slavery became permanent and hereditary. In 1661, a law was passed that made a person's condition of freedom or slavery inheritable from their mother. This established that slavery could be passed down from one generation to the next, and in practice it meant that the children of white masters and black slaves would be enslaved. Another important law was passed in 1682, and said that slaves entering the colony would remain enslaved even if they were baptized as Christians. Slavery was thus explicitly race-based and not based on the fact that the enslaved person was a "heathen."