 In the early-20th century, to institutionalize racial segregation, most southern states adopted the "one drop rule", which defined and recorded anyone with any discernible African ancestry as "black", even those of obvious majority-white or of majority-Native-American ancestry.One of the results of this implementation was the loss of records of Native-identified groups, who were classified only as black because of being mixed-race.See Emigration from Africa for a general treatment of voluntary population movements since the late 20th century.