Franklin D Roosavelt famously said , the only thing we have to fear , is fear itself … the context of which , was in ref to the great depression facing the American people at the time, and that the hardship ahead was tenable if each individual would do their part to weather the storm ..  one may then ask the question what fear actually is .. , has its function changed over course of human evolution , why are we born with some innate  fears that are  biological traits  and others we acquire through exposure or learning , both it seems  serving as a function in our  growth and development and changing culture and traditions.