Are humans naturally violent?

I agree that we have reciprocal altruism (though remember that reciprocal is the only type of altruism you will find outside of kin selection) as well, but disagree as to the nature of human violence. It isn't just defense; it is offense. It is used to gain reproductive status as well as dominance over others.However, as is the case in many nature examples, the fact that it is instinctual does not give anyone the right to violence.

I see your point, but I didn't see the need to differentiate between the two. A carnivore, for example, can obtain food non-violently; it is because the prey will most likely protect itself that the predator must respond. We call this offense, but your body probably sees this as a defense against a defense. Since biological systems favor efficiency, I'm pretty sure that the same neurological mechanism is used to trigger the response.I'm basing this on the similarity of the physiological effects between fear and aggression, but the truth is that I don't know enough about the localization of brain functions to give valid support to this. I'd be flat out wrong if separate devices were triggered, so if you can find evidence for this I'll be happy to learn about it.