The main problem for humans is whether they have total inability to control their desires and instincts. You believe (as humans) that you have surpassed the animals in that and also boast of not letting glimpse their wild and primitive instincts. But it is that, if their lives are based on that.
Eat, breathe, laugh, love ... hate, kill, despise, deceive
All those are instincts that have turned into desires. Relentless desires that collide with each other and become a struggle: the struggle between those who want to live and those who want to kill, those who want to love and those who want to hate.
They have not learned to control themselves, both in the good, as in the bad.