[FLOutdoorsman]

Toynbee's point was without uniting your civ. under a purpose instead of infighting and not collectively repelling an aggressive force is considered suicide.

Which is the case with the Americas, infighting and other tribal differences failed to unite and repel the Spanish.

[GSlob]

Civilizations can die, and have died, by genocide or forced assimilation. Indeed, one could argue that such an end [by applied external force] IS the typical death of a civilization. Genocide is not a suicide.