Fear?

I'm watching Divergent (sci-fi movie--there are five factions in society that you must fit into, one of which is Dauntless. A part of the training to become a full-fledged Dauntless member is to face your fears in some sort of hallucination) and started thinking (as always). 

Something mentioned in the movie was that most people have 10-15 deep fears (i.e. those that are essentially crippling when confronted). Because it's just a movie, I have no idea if this is true. How many fears does each person have? Is it even possible to quantify them, and can something someone has never had to confront or think about be a fear? Fear, then, would be limitless. 

Obviously, we have fear as a survival instinct and it's an emotion imprinted in our brains. The central fear system is the amygdala, which associates fear with whatever stimuli the individual is taught to fear, like snakes, fire, etc. etc. and also is a sort of shortcut of visual processing, which is why sometimes we freak out at snake-shaped twigs before slow visual processing (which goes all the way to the occipital lobe and is milliseconds slower) kicks in to tell us that it is really just a twig. 

But fear has evolved as society has. Clearly our ancestors didn't fear the stock market or car accidents, since they didn't have those back then. How has fear evolved to include social fears like insecurity, and is it still a survival instinct at this point? I'm not downplaying such fears, because social anxiety, insecurity, and others can be very real, very serious, and very crippling. But are they still for survival, and are increases in diagnoses of mental illnesses just speaking toward a greater understanding of the symptoms, are an actual epidemic to society?

Fear is relative. But to what?

What am I even talking about? Do I make sense? 

RL