could it be that the peacefulness arise because human are sleeping? When we sleep, we don't think. Our capacity to judge is almost zero. Our communication is reduced. Silence conquer most of the space. And the only aliveness is the body. So why can't we be peaceful when we awake?

Interesting question and reflection. I wonder this same question myself often, why we can't find a measure of peace and tranquility as a species. Oh well, there are always dreams :-)