War it was a natural course of existence. So long as there were two living being with different origins and beliefs from one another. They were bound sooner or later to fight one another. It could be a matter of personal animosity, religious fervor, or a simple disagreement on political views.
But the reality was that it was a biological imperative. The universe had created so many life forms across the universe, yet despite the vastness of space resources which were needed to survive, thrive and expand would always be scarce.
And with the scarcity of resources came war. Fighting to determine who would control these resources. Such was the nature of life. And the Naraku were no different. It was hard to say where exactly the origin of their species lied.