Yeah, the first one seems pretty deliberate. I doubt the other 2 are direct references to that line, but there is definitely a hook motif throughout the show. I think someone listed them all off once, but I have no idea where that is.
Maybe in order to understand mankind, we have to look at the word itself: "Mankind". Basically, it's made up of two separate words- "mank" and "ind". What do these words mean? It's a mystery, and that's why so is mankind.