Why sometimes Humans are worse than animal?

Human biology makes it such that we have animal instincs of survival along with a brain capable of conscious thought. It is clear that many animals compete with each other to survive. These fights usually involve a mate or a particular animal's territory or a asserting one's position in aparticular matter. Much human violence stems from those basic animal instincts, but the scope and scale, and the degree to which a human will go to succeed, is far greater because of our greater intelligence.

But, of course, in our modern society, it is very hard to justify violent acts because simply surviving is not a major part of a person's life. You can't justify killing someone who steals your food because food is readibly available. You can't justify killing a man who slept with your girlfriend because reproducing is not a high priority. Our instincts to do these things are obsolete in modern society; it's no longer a dog-eat-dog world.

Jam it back in, in the dark.