The birth of the Flood is actually a series of events that can be traced to a time period around 10,000 years prior to the firing of the Halo Array in 97,445 BCE. Following the Forerunner-Precursor War ten million years prior in which the Forerunners eliminated the Precursors from the galaxy, some surviving Precursors turned themselves into a desiccated powder and sent it out into deep space in hopes of being reborn one day. Sometime prior to 107,445 BCE, ancient humans discovered the abandoned ships and powder, and for reasons not well understood, fed the powder to their pets known as the Pheru on the human world of Faun Hakkor. Over several generations the Pheru were genetically altered by the powder, turning carnivorous and feral. This genetic mutation eventually spread to the humans on Faun Hakkor, and after many generations of mutations, became what would be called the Flood today.