If all of us were only violent,
Only the toughest would survive.
Individual humans would be very strong,
But there would only be a few of us,
So we wouldn't pose much of a threat to the other animals.

If all of us were only peaceful,
There would be a lot of us,
But we would actively try to avoid harming other creatures,
So we wouldn't pose much of a threat to the other animals.

If all of us were only violent,
We wouldn't be able to cooperate
Enough to build weapons of mass destruction,
So we wouldn't pose much of a threat to the other animals.

If all of us were only peaceful,
We wouldn't build weapons of mass destruction,
So we wouldn't pose much of a threat to the other animals.

This duality is a double edged sword.
Like any sword, it brings power only to the one who wields it.