This is one of the great questions for the ages. Looking at human history (including that being made to this day,) one would have to say, yes, indeed. That humans have had a violent past is undeniable. We have the capacity to create violence for many different reasons. But is it the basis of human nature, the single defining trait? This I think deserves much more attention. Along this line, we create our own realities by how we live our lives and conduct our personal and public lives. Once someone has been influenced by violence, then the battle begins to not let that become the overriding metaphor. If people use violence as the focus in their lives, it just creates more violence down the road, in one form or another.

Humans must maintain their capacity for violence if for nothing more than to provide protection for their tribes. It is clear not all humans function on the same set of human values and it remains a possibility that, at some point, someone will try to kill you for reasons unrecognized by you; i.e. your ethnic makeup, political or religious views, diet, consumptive patterns, or whatever distorted minds manufacture. 

So, the real question is how is violence best contained without ruining the human experience? And I don't think watching extreme cage fighting is on the list.