The Chinese and Hindu millions who would have starved to death, have been fed, and that's why they're with us to-day.
The natural limit of population is starvation.

The more bread the more mouths, less bread, fewer people.

Europe and the Orient reached the starvation limit before America was settled.

A bad crop meant a famine, and a famine started a plague.

This plague and famine would sweep off a third of the population, and the rest could then raise food enough to thrive on.