When the potato got to Europe, it changed the course of European history. Before the potato, the northern tier of Europe, the population was relatively small and was held back by regular famines caused by failures of the grain harvest.
The further north you go, the dicier it is to grow wheat. And so the center of gravity in Europe, before the potato, was the Mediterranean, where you could grow grain more reliably. The potato did very well at the more northerly areas. It did very well in wetter areas, and it did very well in really poor soils.
So suddenly there was this vast new source of calories that could underwrite the growth of the population, such as never would have happened without the potato.
Since one individual can grow so much food, you need fewer people in the fields to support an urban population. So it's really hard to imagine the Industrial Revolution proceeding as it would without the potato to kind of support it. This New World food remade the Old World.
July 26, 2010
Michael Pollan, in The Botany of Desire, traces the cultural shift from South to North in Europe to the introduction of the potato: