The Prehistoric Dark Ages refers to the times before the Fire Order Era. Those days were the most primitive days, there were no calendars to record times, no cultures or laws to follow, and no papers to record histories. The Prehistoric Dark Ages have a different cultivation system than the modern days.
Representative Race
Innate gods
Ruler
The Great Si Ming
Downfall
The Great Siming was stealth attacked by the his most trusted subordinate when he was in the process of creating the Dao World. After which, the rise of Great Sui, the creation of the totem patterns allowed the mortal livings to stand as strong as the innate gods and Great Sui opened a new era, the Fire Order Era, putting a full stop to the Prehistoric Dark Ages.