If this happened in real life the world would devolve just as depicted here. Survival of the fittest, old morals would go out the windows and those with the strongest survival instincts would prevail. Those with psychotic and sociopathic tendencies would fair pretty well I think.
I actually disagree. I think most responses by mankind in the face of turmoil (say, 9/11) shows that we actually bond and work together to solve the problem at hand. We like to explore fiction that has us returning to our animal instincts, but often in real life the vast majority support each other and look past their surface differences when action is called for.