Meditating further on the phenomenon of persistent wealth, I just thought of another great example: Venice. Seems to me that most of what we remember about Venice--the parties, the gaudy display--comes from the 16-17C. Yet Venice's role as an economic powerhouse pretty much ended in 1497 when Vasco da Gama doubled the Cape and opened an Ottoman-free sea route to the Indies (I remember reading once that the Venetian bourse collapsed on the news, but I can't put my finger on a reference).
Meanwhile, I read in Ezra Klein (Inc.) that among our own non-99 percent, inheritance counts for only 14.7 percent of wealth. Ironically, this means that inheritance is more important to the middle and lower classes. Maybe the real question is not how much of today's wealth is inherited, but how much of tomorrow's.