The alliance negotiated by Sen'tran between the Paragangian Empire [before the shattering] and the leaders of the Earth. Beginning in the time of Jordan Keerigan-Smith .
Sen'tran allows the earth leaders to believe they are central in this alliance, when actually it is just a way of Paragangia keeping control of their relationship with the Earth. At this time Paragangia gives up it's native spoken language and declares English the language of the whole galaxy. Paragangia had given up it's written language much earlier, using instead the technology of the community mind, and before that, dreaming, fo all things we would use written lanuage for with the exception of scriptures.
Paragangia did have written scriptures, in the language which was given up at the time of the earth alliance. late in the series, these records are recovered from HomeWorld and translated by Harris and Allissa. They came to be on Homeworld because they were in the possession of Desmond's Paragan ancestor, who was rescued from Gaia by the founders of LDS HomeWold colony, because the ship carrying the Paragan child and the scriptures, seeking refuge, having been warned of the shattering shortly before it happened, was attacked by Gaia[Leviathan] on his way back to Hell colony.