User blog comment:MeDeoPal/On the Origin of Titans and Shifters/@comment-112.207.19.96-20140428111843

Yes. becouse while hanji was experimenting on eren, eren transformed into a titan for many times, and the ;ast time he went titan in that experimen eren was being absorbed by the titan, and to remove eren from the titan they were forced to cut off eren's front body. but he healed right away.