"If the banjo was commonly known over a large area by 1750, as I assume, then it must have been introduced two or more generations prior to 1750. It is likely, therefore, that the amalgamation of music from Africa and Europe, and the adoption of the banjo by whites, began during the early colonial era, from 1620 to about 1670 when the distinction between indentured servants and slaves was not clearly defined in law. This was also a time when 'black and white joined together to drink, gamble, frolic and fight.'
"The gourd banjo was known and described earlier in the West Indies and South America than in America; however, the banjo did not survive in those places as a folk instrument. Early slaves imported to the West Indies and South America were mostly male, and black families did not begin to be established there until much later than in America. Berlin asserts that free black communities were being established on the Chesapeake by 1650. Communities consist of families; therefore, free black families were being formed alongside those of white servants and wage earners. Families are, I believe, the necessary mechanism through which banjo playing, dance and other folkways are passed from one generation to the next."
http://banjohistory.com/article/detail/1_gourd_banjos_from_africa_to_the_appalachians