Agreed. Some interstellar civs could've come & gone a zillion years ago. (Maybe "gone" in the sense of subliming in the Culture novels.) The chance of two such

Agreed. Some interstellar civs could've come & gone a zillion years ago. (Maybe "gone" in the sense of subliming in the Culture novels.) The chance of two such civs being still extent and still interested in hanging around seems small. Doesn't do much for sci-fi tho.