Trying to remember a manga/anime

I can't remember if it was a manga or an anime.

The basics of it are, a regular human was hiding with an old man somewhere deep within a city/ship/something. But, the old man dies, and so the human boy goes out to find food. He is found out by the rest of the "humans", who have been genetically modified to be super-human, need little to no food, etc...


I believe they were traveling thru space, fighting some huge-*** god-like monster things. I can't quite remember exactly.


Any of this sound familiar to anyone?