Well, what if they did?

I think that I have been incorrectly assuming that this subthread was about whether, in 2017, we could tell which of two things had happened -- either "there was a time when there were only 40 pairs of humans on all the earth", or "everyone today is descended from a 40-pair group that may have coexisted with others but for some reason those others died out."

If in fact we're instead talking about whether we can make any distinctions whatever between the two situations, even though we know now that whichever actually occurred, humanity didn't go extinct, then I retract my objections.