User blog comment:MeDeoPal/On the Origin of Titans and Shifters/@comment-198.7.247.194-20141026004857

There was an expedition into the ruins of a city belonging to an ancient civilization that mysteriously disappeared. Within the city ruins was an unbroken circle of great stone walls that sealed off its interior. When the wall was opened it's interior revealed the bodies of numerous giants all in a comatose state (since Titans have slow metabolism they could survive extended periods of suspended animation). When the archaeologists continued their  exploration their scent signalled to the Titans that food was available, waking them. To combat these biological threats the government began creating bioweapons, devices that could change human soldiers into Titans. All was well until one scientist went mad and permanently changed himself into a Titan. (He is the muscled titan who knocks down the wall in the first episode) He became the leader of the Titans and the most powerful antagonist in the anime series. Titans possess internal sexual organs. The differences between male and female Titans cannot be not be noticed by humans. The Titans were originally selectively bred by the ancient civilization as beasts of burden hence their variation. Their masters were a warlike people who would unleash them onto the battlefield allowing them to consume human flesh. Eventually the surviving humans took up residence within the interior of the ruined city, shielded by the ancient walls of the lost civilization. How the lost civilization went into ruin could be any number of reasons... Disease and political unrest to name a couple.

-Jimmy Ke