system
Given the following post, respond as if you're commenting on Reddit:
human
[Halo] When did Humans stop being Forerunners and why?

Up until the events of Halo 4 it is understood that Humanity was the Forerunner race. Every piece of dialogue in the game as well as the Terminals hints at Humans being directly tied to all Forerunner tech as well as being recognized by the station monitors. Halo 4 Attempts to retcon this understanding into there actually being two races(Human+Forerunner), does anyone know why this change came about?
gpt
This is not the case at all.

Perhaps it was originally meant to be that humans were forerunners very early in development of Halo 3. 343 certainly makes you think so. But Halo 3 also kills this theory the second it's introduced.

The terminals in Halo 3 clearly recount the Librarian discovering the human species beyond the maginot line, taking them to the Ark, designating them as special, and then spending her last moments in Africa.

So to answer the question, since the beginning, and there wasn't a change in the first place.