Extremes Meet

On the face value I could never understand the proverb "Extremes Meet" Mind kept on Rolling for the answers of many questions...

Why is bell curve symmetric? And in the bell curve why middle is important and not sides?

How coolly we have allowed the Earth to get Warm?

Why do human beings kill other human beings in the name of Religion when no religion preaches it?

Why should family honour lead to killing of the siblings or blood relations?

Why organized religion is not in sync with the law of Nature?

If we acknowledge that devastation caused by floods in Bihar-India, was caused by Koshi River changing its course.... Do we Humans not cause more devastation by changing our course which has been laid down by Nature?

Why are we so miserable when we have progressed much more in the last century compared to the entire history of the Mankind?

MIND wanders..... is it because we have chosen extreme (outmost) instead of Middle Path?