For as when much superfluous matter has gathered in simple bodies, nature makes repeated efforts to remove and purge it away, thereby promoting the health of these bodies, so likewise as regards that composite body the human race, when every province of the world so teems with inhabitants that they can neither subsist where they are nor remove elsewhere, every region being equally crowded and over-peopled, and when human craft and wickedness have reached their highest pitch, it must needs come about that the world will purge herself in one or another of these three ways, to the end that men, becoming few and contrite, may amend their lives and live with more convenience.

Book 1 Ch. 5 (as translated by Ninian Hill Thomson) - Discourses on Livy (1517)