:') PreColumbian Central America (including Mexico) shows population peaks three or four times (or more) estimated to exceed those of the postcolumbian era until the 20th century -- followed by collapse. Could be due to the climate cycle (which wouldn't be that surprising), but it could also be an indirect consequence of that same cycle -- IOW, introduction of disease germs from the Mediterranean basin.
A regional catastrophe.
Historical Review: Megadrought And Megadeath In 16th Century Mexico (Hemorraghic Fever)