[Cicero]

Yes, it's an interesting article. And not all that surprising, really. The majority of the population at most times consisted of peasants and serfs, and there's no reason to think they would have all been killed or ousted when new conquerors moved in.

Some French historians of the annales school have pointed out that there's more continuity over the centuries when you look at peasants' huts and villages than there is in manors and castles, because invaders usually go after the manors and castles. The fighting takes place mainly within the fighting classes, which are the nobility and gentry. Peasants get killed, but there's no particular incentive to wipe them out as there would be with competing nobility.

[Snerfling]

majority of the population at most times consisted of peasants and serfs, and there's no reason to think they would have all been killed

The 'serf' survival strategy is still with us today in the form of bureaucracies. The key to success is to never stand out amongst the rest ie the even hedge theory. Only the top level players win or lose.