User blog comment:NickFusi0n/A Theory on The Coordinate and The Wall Titans/@comment-25358468-20140522214517/@comment-3074300-20140523151717

So... apart from this theory I had another one. You know how in Chapter 57 it's revealed that if a Titan eats a Titan Shifter the Titan will regain human form and obtain the transformation ability? My guess is, Grisha, Eren's dad was originally a Titan Shifter himself, plus he also possesed the Coordinate. When he injected Eren with the serum Eren went mindless and turned into a titan. Grisha then allowed him to eat him, making Eren regain human form and obtain the Coordinate plus the transformation ability, then lose memory of the event. Which explains why he wrote "My father was... by me" and then he grieved.

However, something doesn't pass. Remember the titan that ate Eren at the end of Episode 5? The one that Eren later punched his way out of? How come that Titan didn't turn back into a human when he ate Eren?

Of course I could be wrong and Grisha could have passed down the Coordinate to Eren and then disappeared (Possibly being hunted for also having it... although that's unlikely). In addition to that, I've heard rumors that the text actually states "I was ... by my father" due to a mistranslation and a confusion with the japanese grammar. This is also unlikely considering this wiki itself states that the text says "My father was ...by me"