It has been argued that all musical compositions are derivative......to a certain extent.....in one way or another ?
Derivative... or duplicative. Especially with regard to simpler tunes, I don't find it at all unlikely that they could be conceived independently many times. I mean, if somebody in 1830's Ireland (e.g.) composed a tune, does that somehow invoke a magical spell that makes it impossible for anyone else to imagine the same melody without hearing his (or her) "original"?