User blog comment:BlouseGirl/Unanswered questions that still need answering/@comment-27441457-20160701040352

3: My guess would be some sort of super-soldier genetic experiment long ago in humanity's history. Somehow, human science figured out how to make super-soldier modifications inheritable, creating a bloodline of born soldiers. It would fit in nicely with the other theory that Titans are biological weapons from a bygone era. But this raises the question, if humanity's scientific advances could accomplish huge things like this, what happened to bring it all down?

2: I never thought about it and you're totally right, the "subjects of Ymir" could have completely disappeared in the 60 years she was wandering as a Titan.

As for who Ymir herself is, she could be very much like Historia was: an illegitimate child of a royal family who was rejected for her existence. Not the most incredible of backstories considering we've seen it before, but it would explain (shipping aside) why Ymir was so drawn to Historia.

1: My best guess would be that Grisha discovered (or was searching for) a way to overruly the "Reiss lock" on the Coordinate so that it could be used without the influence of the First King's ideology that's been stopping the Reiss family from doing anything useful for 100 years. But hopefully it'll also hold a nice, big, chapter-long plot dump about what started the whole mess that is the Titans.

It's still hard to believe we're so close to finally getting there, after so many years o_o