[Fyron]

Its a mod setting, in Data\Settings.txt. It basically creates free population on every newly colonized world. At one point, this population was always the native type for your empire. This screwed up colonization of different-atmosphere planets with aliens, since it would add a few million oxygen breathers to methane worlds where you had loaded methane breathers on your colony ship. This is primarily why some mods, such as BM, set the value to 0. There was talk of a fix, where it would instead add pop of the type on the colonizer (if there was any), but I don't recall if it made it into a patch or not.