But we don't know for sure since we a "born" into this universe without any knowledge of it. We don't know if our Golden Age with the Traveller was not a time when we went outwards destroying other civilizations. We are told that the Traveller is good but maybe the other species in the Destiny universe are just trying to stop a "god" that has only brought destruction and now has an undead army that exists to kill. Guardians are the perfection of Oryx's Sword Logic. We even grow stronger the more we die (that is even if we die in a mission we get resurrected and then finish it etc in hopes of getting better gear.)