There should have been a Human Disciple Of The Witness In the final mission area of Arrivals(after you kill Nokris), we see a scene of all Sol species kneeling to the pyramids, including Humanity But killing a Human in PvE would be too dark, and effect thier ESRB rating, even though it would make the game more dynamic and interesting, and more realistic In Mass Effect, Reapers are the main enemies, but there is still a shadowy Human organization fighting against Shepard and The Alliance(Cerberus) But even the Techeuns we don't kill them, we save them, by shooting them in the face