Ancestors

By approximately 150,000 BCE, humanity had achieved a considerable level of technological sophistication, achieving interstellar travel and colonizing planets along the Orion Arm of the Milky Way Galaxy.

History
Having moved their civilization outward along the Orion Arm, presumably to flee Forerunner control, humanity formed an an alliance with the San 'Shyuum species, based on the planet Charum Hakkor. At this point, humanity's technological advancement rivaled that of the Forerunners, with the humans using Precursor artifacts to support their structures and installations.

This civilization encountered the Flood in approximately 110,000 BCE and, after discovering the parasite's true nature, went to war against it. Eventually, humanity sacrificed a third of their total population, implanting them with destructive, artificially programmed genes used to assault the Flood on a genetic level. After losing many planets to the Flood, humanity desperately invaded a minor sector of the Forerunners' domain. The Forerunners responded violently to this aggression and waged war with the biologically similar human species. Stretched thin due to fighting two wars at once, the humans were defeated at the hands of the Forerunners, led by the Didact. However, due to humanity's actions, the Flood was driven off the galaxy for nearly ten thousand years.

As punishment, humanity was devolved and reduced to a pre-technological state and were exiled to their homeworld, Erde-Tyrene, where they were overseen by the Librarian. However, the Forerunner victory proved disastrous for the galaxy as the humans destroyed all their research data and physical evidence concerning the Flood, including their cure to stop the Flood. Bornstellar Makes Eternal Lasting speculated it may have been humanity's last act of revenge to leave the Forerunners unprepared to face the incoming threat that led to the firing of the Halo Array.

Forced to start again, the collective human genera tried in vain to reattain their former glory, with some human communities establishing wooden cities and steam-powered waterborne vessels under the instructions of the the Librarian. Most humans, however, lived in Tier 7 tribal communities, such as the one that was encountered by the Forerunners during the construction of the portal the Ark in eastern Africa. After the activation of the Halo Array, the human civilization regressed once again, and would remain in a Tier 7 state for the next hundred millennia. As of the 26th century, most artifacts and records of this former civilization had been lost to time.

List of appearances

 * Halo: Cryptum