I suspect that after all the hype has died down, Brexit will have as much impact on "western civilization" as the Y2K bug did 16 years ago. (ie, virtually none.)
Y2K created boom in IT. Nasdaq is bellow the peak in achieved 16 years ago and the effect from the boom/bust is still lingering today. The boom after 2003 till 2007 was short-lived and fueled by housing boom. American, Japan, and European real salaries did not recovered to the levels of 1999, almost entire generation. And we do not need to go too far into history when common market disintegrated and what was the economic cost. USSR is one of the example and Russia and all its ex-Soviet republics did not recover from this shock. UK / EU relationship is not much different, UK was a part of EU economic zone for 40+ years. UK (contrary what they think) is not economically unique and different from Russia when its economic zone disintegrated.