heh.. she's 5 now but I still remember....
most infant mammals have an almost intoxicating scent.. puppies, kittens, foals, humans alike.
in the grand scheme of life it makes sense to help insure survival...
also, the chemistry involved means that one's own baby smells best to you, and someone else's not so much. this is true from penguins and deer to humans as well.
but yeah, it's a lyric you'll "get later" if you're not at that stage of life, or maybe won't get at all if you never have the experience. not the first time he's done so after all.....