I have always been into full contact aggressive sports...too old now tho. I use dogs to hunt prey and have a full bite trained on human targets dog I hire out for property and human protection. I enjoy the training and the work, so does the dog. Is aggression just part of what we are, can we ever evolve past it? I heard of societies that have no vocabulary for war and have no evidence of being in a war or fighting. They were utilised in WWII I think and were taught aggression to good effect - after the war they went back to zero aggression.