It is the world’s fourth-most-important food crop, after maize, wheat and rice.It provides more calories，more quickly, using less land and in a wider range of climates than any other plant.It is, of course, the potato.The United Nations has hoped that greater awareness of the merits of potatoes will contribute to the achievement of its Millennium Development Goals, by helping to reduce poverty and promote economic development.The potato promoted economic development by supporting the Industrial Revolution in England in the 19th century.It provided a cheap source of calories and was easy to cultivate, so it liberated workers from the land.Potatoes became popular in the north of England, as people there specialized in livestock farming and domestic industry, while farmers in the south concentrated on wheat production.By a happy accident, the concentrated industrial activity in the regions where coal was readily available, and a potato-driven population boom provided ample workers for the new factories.Friedrich Engels even declared that the potato was the equal of iron for its “ historically revolutionary role ”.In the form of French fries, served alongside burgers and Coca-Cola, potatoes are now a symbol of globalization.This is quite a change given the skepticism which first greeted them on their arrival in the Old World in the 16th century.They were variously thought to be fit only for animals, to be associated with the devil or to be poisonous.They took hold in 18th- century Europe only when war and famine meant there was nothing else to eat； people then realized just how useful and reliable they were.As Adam Smith, one of the potato’s many admirers, observed at the time, “The very general use which is made of potatoes in these kingdoms as food for man is a convincing proof that the prejudices of a nation，with regard to diet, however deeply rooted, are by no means unconquerable.” Mashed, fried, boiled and roast，a humble potato changed the world，and people everywhere should celebrate it.