Board Thread:Theories/@comment-30785465-20170219162046

Titans are weird creatures. Humanoid giants that eat humans. Although they eat humans, they don't actually need to. They ignore all other organisms and only pay attention to humans. They are completely self-sufficient, getting their energy from sort sort of photosynthesis-like process of using the sun's energy and almost enter a sleeping like trance at night. It is also seen that Titans can't even digest the humans that they do eat. They have stomachs that would appear to function like a normal one including the digestive tract and everything; except they lack a digestive tract, explaining while they regurgate the humans they eat into a big sticky ball of their stomach contents. They can go for hundreds if not thousands of years without eating humans. Before the year 845 when the Colossal Titan and Armoured Titan breached Wall Maria, humans had not even come into physical contact with Titans.

There is an actual reason why they eat humans. You know how the Titan Shifter ability is passed down generation to generation by injecting the inheritant with a fluid made up of a human's spinal fluid into a person turning them into a mindless Titan and they consume the Titan Shifter thus gaining their powers and memories? The reason Titans eat humans is because they want to escape being a Titan, suggesting that they may have some sort of awareness. They eat humans in the hope that one of them will be a Titan Shifter so that they may return to their human form. Although the chance of the humans that they eat is a Titan Shifter is extremely rare, it has happened in the past. When Ymir was in her mindless Titan form, wandering the desolate lands of Paradis for sixty years before coming across humans; she attacked Bertholt and Reiner when they were younger and ate their friend who was a Titan Shifter, thus explaining how she became a human once again.  