Larry Graham is also a professional grade shit-talker and has given several different version of his "discovery" of slap-bass.

HOWEVER: It is fairly certain that he was the one that really did introduce the slap and pop technique. He might not have been the first to slap a bass string, but that unique 'slap-and-pop' is most likely his creation.

AND, He is incredible good at it.

His old instruction video is still a goldmine.