User blog comment:MeDeoPal/On the Origin of Titans and Shifters/@comment-164.151.4.18-20140710132414

I think Erins father injected him with the mark, allowing him to control titans. When the wall was breached Erins's father knew what they were after, and entrusted the forum with his son. He most likely went into hiding because they were after him, hence the attack on that town. I'm thinking the reason titans eat humans is because they are searching for the mark this way.

The Ape titan... he may be one of the originals and is now looking for the mark because it makes humans a threat. He could also be the one giving the orders to Reiner and the titan peeps. If he can control titans, he must have some form of mind control on humans with titan powers too. Also, if Reiner is as strong minded as the manga wants you to believe, why is he the only one going 2 minded? It could be that he's the only one strong enough to fight the 'warrior' mind control. But that's very far fetched!