The Progenitors were the first species to begin the uplift culture currently common in the Five Galaxies.
The only survivors of a galaxy-wide war nearly 2 billion years ago, the Progenitors first uplifted races to create company for themselves. The Paen of Loneliness is composed during this time.
The Progenitors eventually retired as a species, leaving galactic society to be managed by their client races. (2.3 bya)
However, galactic society nearly collapsed, slowly reviving with the aid of the early Galactic Library.