tsb wrote:It's a problem to which I have no answer
That's why it is the most pressing problem in the world today. Why do we do what we do?
The science that I believe has the best approach to finding the answers to human behavior is that of Ethology which is the study of how an organism adapts to its environment. To go back to root causes and basics is always the best way to learn something, and that is what ethology does. To understand behavior Niko Tinbergen, one of the founders along with Konrad Lorenz posed four questions that had to be answered to reach understanding. These were:
Function — How does the behaviour affect the animal's chances of survival and reproduction? Why does the animal respond that way instead of some other way?
Causation — What are the stimuli that elicit the response, and how has it been modified by recent learning?
Development — How does the behaviour change with age, and what early experiences are necessary for the animal to display the behaviour?
Evolutionary history — How does the behaviour compare with similar behaviour in related species, and how might it have begun through the process of phylogeny? Phylogeny being evolutionary change through time.
Names you might recognize that have contributed to this science are Jane Goodall, Diane Fossey, and Louis Leakey.
Concerning aggression an excellent book is Lorenz's "On Aggression"