actually, the final argument isn't so much about galaxies forming. for a civilisation to have formed early enough to affect all of the observable universe with

actually, the final argument isn't so much about galaxies forming. for a civilisation to have formed early enough to affect all of the observable universe without time/ftl travel i think that they would have to exist before atoms existed (ie when the universe was still a primordial "plasma", during "inflation", assuming, of course, current models, although this general constraint is fairly strong, given the microwave background uniformity, although(!) see below). now you can argue that the idea that atoms are necessary for life is an anthropomorphic bias :o) but really the problem is that very little of anything had structure at that point. and for life i think you do need some kind of order. this is related to why the microwave background result(s?) with large-scale anisotropies was(were?) so weird (and, if i understand right, have since been discounted) - http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation#Low_multipoles_and_other_anomalies http://en.wikipedia.org/wiki/Cosmic_microwave_background_rad...