So the Movie kinda spoiled the Titan Origins I think. SPOILERS.
Honestly, if this is what the Manga is gonna reveal too, then I'm not surprised since I've started to recently think that this might be the case.
military experiments gone wrong from a century before.
Read this on the wiki site for Part 2 of the film. The films sound absolutely trash but I'm also a bit worried if they have spoiled it.
My THEORY has been that when Eren gets to the basement he will find out information that reveals that thousands of years ago the current world, our world, did a experiment to create super soldiers. It went wrong and the world went to s..t. Eren's dad and the Beast Titan and others all come from our period of the world. The World Leaders or that remained created the walls and decided to basically pull a VILLAGE twist with keeping people in medieval like times or something. When Eren's dad came to the walls he ended up giving his knowledge to them like the 3D movement gears.
This is why the Beast Titan was surprised by the technology because it comes from their village or part of the world and no one else should have access to it and that revealed to him it was Eren's dad who gave it to the Survey Corps and stuff.
I imagine Reiner's, Annie's and Bert's village actually a broken down city or what's left of the past modern world. Broken skyscrapers and s..t. I bet that's what the revelation and twist for AOT will be.
Love breeds sacrifice, which breeds hatred. Then you can know pain - Pain