Their ship graveyards are where galactic history starts — a detail Carl hears without comment.
The Primals surface in Mordecai's account of Syndicate history. When the Escape Velocity found the wormhole to the first system, it was a Gleener scientific crew investigating a Primal ship graveyard there that came across the Vog Generation Ship, and a few hundred cycles later the The Syndicate existed. Mordecai relates this as ordinary background, unaware or unremarking that he is talking to a crawler who chose the race for himself.
The progenitor race whose derelicts seeded Syndicate history.