To quote Crosby, It is crudely true that if man's caloric intake is sufficient, he will somehow stagger to maturity, and he will reproduce. And New World food was far more caloric than Old World food, which is the central reason that the world population doubled between 1650 and 1850. Plants like corn and potatoes could grow in soils that were useless for Old World crops. Potatoes were actually introduced to Europe as an aphrodisiac, but it turns out that you have to distill those potatoes into vodka before they have the desired effect. Anyway, if potatoes are an aphrodisiac, the Irish quickly became the hottest people on Earth. An acre and a half of potato cultivation could feed an Irish family for a year, and the average Irish worker often ate ten pounds of potatoes every day. Surviving primarily on potatoes, the Irish more than doubled their population between 1754 and 1845, when the potato famine showed up and ruined everything.