Board Thread:Manga/@comment-7278867-20170312084406/@comment-28516743-20170402212612

I think it depends on how often a shiter uses their powers. It's quite likely that Ymir Fritz used her powers very often, as she built cities for her subjects. Using her titan powers that often probably exhausted her body very quickly, and after thirteen years, her body couldn't handle the power of the Titans any longer, and so she died. Grisha, on the other hand, rarely used his Titan shifter power. The only time we ever see him shift was the day Wall Maria fell, when he went out to retrieve the Coordinate from the Reiss Family.

Also, what if the tree that Eren is lying under at the beginning of the series the same tree that appears in drawings depicting Ymir Fritz? (The tree where Ymir picks the apple from)