What do people fear most in life?

A very simple, almost naive, answer will be "FEAR OF THE UNKNOWN". This fear manifests itself in different forms under different situations. Although, collectively we have progressed a great deal to minimise these fears over the past hundred or so years, through our inventions, but the human brain hasn't been able to keep up with this progress. As a result, although we can see the absurdity of our fears but we still can't convince our mind to allay these fears.