User blog comment:The Milkman/Reaper Logic/@comment-5124423-20120521161512

The Reapers are not the same synthetics as the Geth. The Geth are pure machines whereas the Reapers are made up of organic material. They store the life of the highly advanced civilization, leaving the "not-so-advanced" behind so that they can grow. I guess this is a form of prevention that the new civilizations are not totally dominated by advanced species like the Protheans -- which in fact, did dominate other species and if their domination over them could not be arranged, they simply wiped those species out. The Reapers thus "save" the lifeforms of the Milky Way. And if a hihgly advanced civilization, dominating all other species in the Milky Way Galaxy, creates pure synthetics that are stronger than their creators, those synthetics might wipe literally ALL organic life out. If the highly advanced civilizations cannot create those "Killer Machines" and are instead harvested by the Reapers, the endurance of organic life is assured. It seems to be all about preservation.