Hey, just to show you there are no new arguments under the sun, here is the very first paragraph of Roger Abrahams's 1974 book Deep the Water, Shallow the Shore:
"There are certain musical types that seem to arise only in areas in which Afro-Americans and Euro-Americans perform together or at least witness each other's performance forms--Jazz, jody calls, cheerleading, to use some American examples. The sea shanty is one of these. In Chanter-response performance type, with a high degree of voice overlap and interlock, these work songs are more in African singing style than European (with the possible exception of Celtic singing in groups). Yet they arose and thrived at a time when Afro- and euro-Americans and Europeans worked together under sail, and it seems clear that it was this combination of ethnic groups pursuing a common purpose that provided the situation under which these songs thrived."
Roger then provides an excellent five-page survey of the scholarship on black contributions to shantying; from Sharp, who was skeptical but admitted that some shanties had black influences, to W.F. Arnold who, in a 1914 book called Songs of Sea Labour proclaimed that the majority of shanties are "Negroid" in origin. The origin issue has long been a vexed question, because the hard data are simply not there to be found.