'People have pointed to a widely sung folksong, "Pretty Polly," as exemplifying the form, if not the scale or lyrical subject matter, in white tradition.'

I'm interested in the history of 'Pretty Polly', and in particular its evolution from the English broadside ballad 'The Gosport Tragedy' / 'Cruel Ship's Carpenter'. Sharp collected the song in both its archaic and more modern form during 1916-18, and my impression is that it was usually younger people who sang the 'Pretty Polly' version, possibly because it was new and fashionable. Josiah Combs wrote in 1925:

'One of the best examples of the harrowing of the folk-song in the hands of the banjo picker is ‘The Gosport Tragedy’, commonly known as ‘Pretty Polly’. The traditional airs of this song are strangely beautiful, but are hardly to be recognized when played on the banjo.'

Combs put the transformation of the song down to its adaptation for the banjo, but that alone would not explain its transformation from a standard 4-line stanza folk song to the AAAB and AAB versions that superseded it. Which makes me wonder - is it possible that the change of form was brought about by African-American musicians, and are there any examples of members of that community having sung it?