considered socially as a "half-breed" or breed and stigmatized by both communities. The 20th century one-drop rule made it relatively difficult for anyone of known Black ancestry to be accepted as White. The child of an African American sharecropper and a White person was considered Black by the local communities. In terms of the economics of sharecropping, such a person also would likely become a sharecropper as well, thus adding to the landholder or employer's labor force. In short, this theory suggests that in a 20th century economy that benefited from sharecropping, it was useful to have as many Blacks as possible. Although some scholars of the Jim Crow period agree that the 20th century notion of invisible Blackness shifted the color line in the direction of paleness, and "expanded" the labor force in response to Southern Blacks' Great Migration to the North. But, others (such as the historians Joel Williamson, C. Vann Woodward, George M. Fredrickson, and Stetson Kennedy) considered the one-drop rule a consequence of the need to define Whiteness as being pure and justifying White-on-Black oppression. Over the centuries when Whites wielded power over both Blacks and Amerindiansand believed in their inherent superiority over people of colorthey created a social order of hypodescent, in which they assigned mixed-race children to the lower-status groups. They were often ignorant of the systems among Native American tribes of social classification, including kinship and hypodescent. The Omaha people, for instance, who had a patrilineal kinship system, classified all children with White fathers as "White", and excluded them as members of the clans and tribe, unless one was formally adopted by a male member. Tribal members might care for mixed-race children of White fathers but considered them outside the hereditary clan and kinship fundamental to tribal society. The hypodescent social construction related to the racial caste that was associated with African slavery and the conditions of the slave societies. It was made explicit by Virginia and other colonies' laws as early as 1662. Virginia incorporated the Roman principle of partus sequitur ventrem into slave law, saying that children of slave mothers were born into their status. Under English common law for subjects, children's social status was determined by the father, not the mother. But the colonists put Africans outside the category of English subjects. Generally, White men were in positions of power to take sexual advantage of Black women slaves. But, historian