Simplify the following text for a Grade 9 native English-speaking person.
Original: The six editions of his An Essay on the Principle of Population , published from 1798 to 1826 , observed that sooner or later population gets checked by famine and disease .
Simplified: There were six editions of his An Essay on the Principle of Population , published from 1798 to 1826 . He said that sooner or later population gets checked , by famine , disease , and widespread mortality .