The Origin of the Big Sister(s)
In the First Bioshock at the end of the game, wouldn't Rapture be atleast 75% abadoned? Most of Rapture's citizens are dead or escaped somehow, but what about the Scientists and Engineers? After beating the game I figured there would be no humans in Rapture to keep the city thriving in new technology considering an example of Professor Julie Langford who was a expert in plant science but unfortunately died by Andrew Ryan. After exploring the factory where the Big Daddies where created and find the Big Daddy suit to get into, I figured there is no one around to manage the factory. But where does the Big Sister come in? How was it created? Maybe before "The Fall of Rapture" scientists and engineers were creating something far more powerful and superior of special beings than the Big Daddies, the Big sisters were possibly a better model of (whatever species you want to call them) Big Daddies. Maybe it was kept locked up all that time during the first game and in the 7 years that have past since the events of the first game it somehow was released. Or was it being created in those 7 years?
Hints in the Game Informer thread