They arrived on a Dutch ship that had captured them from the Spanish. These approximately 20 individuals appear to have been treated as indentured servants, and a significant number of enslaved Africans even won their freedom through fulfilling a work contract or for converting to Christianity.[18] Some successful free people of color, such as Anthony Johnson, acquired slaves or indentured servants themselves. To many historians, notably Edmund Morgan, this evidence suggests that racial attitudes were much more flexible in 17th century Virginia than they would later become.[19] A 1625 census recorded 23 Africans in Virginia.