The citizens from Rapture have gone mad.
A scientific discovery upset the balance of the society. Two scientists studying ocean-floor dwelling creatures discovered a species of sea slug that could secrete stem cells. These could be used to enhance one's body, improving physical or mental capabilities, curing diseases and healing injuries. A young entrepreneur named Tenebaum invested early on in the research to gain control over the material. The substance, dubbed "ADAM", became so sought after in the society, that it became the dominant currency of the city. A "full-scale genetic arms race" broke out between Ryan and Tenebaum as Tenebaum's monopoly on ADAM threatened the current social structure. Ryan eventually won, but everyone in the city was permanently changed. It was discovered later that ADAM could be used to modify one's body, combining technology and mutations to adapt and survive the conflict, but losing their humanity in the process. During the conflict, all natural sources of ADAM were destroyed, which eventually resulted in a major shift in the "ecology" of the city, as all inhabitants had become biologically dependent on ADAM to survive. Attacks with biological weapons lead to the downfall of Rapture's society, and the city fell into a state of disrepair.
