- last post: 01.01.0001 12:00 AM PDT
There are other possibilities. If the Flood were being researched for whatever reason then they might have been researching other species.
Personally, the theory I'm following at the moment is that long ago the humans were the only true civilization in the galaxy. They were the forerunner, a proud and decadent race that never once thought they could ever do wrong.
Having mastered the machine, strange energies they expanded their experiments, working with the very foundation of life itself. They began creating servitor species, bred to survive in harshest environments, to protect them and perform hard labor where machines would be less efficient.
It would be a new era for the Forerunner topped by their one new experiment. They were to be immortal, the discovered a lifeform with vast regenerative properties and were attempting to extract the genes that made it so resilient. They did not foresee the danger. How could they? They were gods. One day that particular experiment escaped and brought the forrunner to it's knees.
The triggering of the Halos was their only option to save what was left of the universe. A last lone human aboard the Halo Installation 04 stopped and hesitated, realizing by activating the Halos he would destroy what little human life remained. He has an idea, there is a slim chance for survival however, Guilty Spark, the AI guardian of Halo 04 annihilates the human when he begs for time, taking the index for himself and activates the ring. Years later, confronted by the Master Chief the AI becomes confused between the two events and begins talking to the Chief as if he were his ancient master.
The Halos go off and humankind is nearly eradicated, all except for those huddled away in a special chamber in a forerunner facility on a small world called "Earth". Meanwhile, lightyears away the races of the covenant prosper and begin to gain sentience, exploring the laboratories they were created with or escaping out into the wild. Milennia later the Prophets begin to gather together the races and takes the role the Forrunners were meant to be... the God Kings of the servitor races.
Then... the Covenant encountered Earth and the Prophets, for the first time, knew fear. Their masters had returned.