It's just not a single cohesive civilization. Though it would be fascinating. Imagine if our world were seeded with life and terraformed (which now would be quite the misnomer) to be able to host the human-like spawn of a human-like "civilization" that very slowly and discontinuously spread through our corner of the galaxy. That would be quite something, though how would we know unless the parent civilization left us clues to this? And they would have to, if they wanted us to eventually further spread the species/whatever.
Or maybe we are sui generis and about to embark on such a program. Or maybe we are about to run headlong into another's such program, possibly causing conflict. Or maybe it's all much too unlikely. I wouldn't know.
