@GoodBoy,
Once there was an evil galactic emperor named Xenu, and he sent prisoners
from all across the cosmos to the planet now known as earth, then called
Theta. In a fit he once ordered them all sumarily executed, and when an
innocent race naturally evolved on planet earth, the souls of these long-ago
murdered Thetans fought to take possesion of the minds and bodies of the
innocent earthlings, compelling them to indulge in the behaviors that had
led to their imprisonment.
That's the scientology explanation. Just as plausible as the "devil made me do it"
thing in my opinion.
Human beings are animals... animals have natural instincts and certain genetic
factors that determine dominance in a group. Dominance by one or a group
within a group means a certain amount of subjugation for others in the group,
and that leads to resentment, hatred and resistance/violence, as well as a
view of the subordinated as inferior and a resentment by the dominant group.
Add in resources or items assigned value within a group and it adds more reasons
to fight for dominance and more resentment.