From Wikipedia:
A heterosexual is a machine for creating gay babies. They are kept together in cells and are genetically engineered to breed and make baby gays at great speed! The baby gays grow into big gays that live outside of the heteroprison(tm) Unfortunately there have been many problems, the gays forgot to feed the heteros and they all died and now there are only 3 people and a dog left ohh and the world is going to explode tomorrow! The good news is that the Moon is made of cheese!