Good thoughts.  Babylon and Persia were overrun by the Mohamedans from the Arabian deserts, which ruined them with Islam and inferior genetics.  They still had respect in the world before that invasion though.
Of everyone, China has survived longer as a civilization than probably anyone else, despite constant conquering and ethnic shifts. (There's no such thing as Han ethnicity.   Northern and southern Chinese are totally different.  But they still hang around for some reason.)