Wasn't sure exactly where to post this, but here should be good enough. This contains some hints about the walls and humanity's history in SnK. This isn't spoilers since none of it has been talk about in the manga itself, but it might cause readers currently up to date on serializations to reevaluate their theories.
http://calorescence.tumblr.com/post/...f-the-japanese
Quite an interesting read in either case.