User blog comment:MeDeoPal/On the Origin of Titans and Shifters/@comment-121.54.44.182-20150428114216

Okay, I also have a theory and I will share it here. In the beginning there were two kingdoms at constant war. The first kingdom, managed to create humans that can turn into Titans, they were intelligent, unique, and served as soldiers. These Titans were used to defeat or atleast make the enemy kingdom surrender. With this loss, the enemy kingdom somehow stole the formula to create Titans or managed to create their very own. They made mindless Titans, probably out of their very own people. They were "programmed" to kill humans. Also, they can sense if a Titan is a shifter. This might be their very goal, to eat humans in the luck to eat a shifter, for it is the only cure for being a mindless Titan. Anyways, these mindless Titans were unleashed by the enemy kingdom for revenge. This event drives humanity to the brink of extinction. But before being completely destroyed, the other kingdom was saved by the intelligent Titans, sacrificing themselves to create the walls. Remnants of the enemy kingdom might still be existing outside of the walls, this is where Annie, Reiner, and Bertholt came from. I recommend that you watch AOT's second ending song, that served as the foundation of this theory. I think their whole history is written inside the walls. -BR. VI. BA.