Peasants and Potatoes

"More efficient methods of land use [in 19th century Europe] were accompanied by the rapid development of improved strains of wheat and other traditional crops... Far and away the most important of the new crops, however, was the potato (also originally imported from America), which could be grown on poor soil, was comparatively insensitive to the vicissitudes of weather, and yielded from two to four times as much food as grain crops. Although cultivated throughout Europe, the potato became the staple diet of poorer peasants in the northern and central regions along a broad front from Ireland to Russia, a dependence which was to prove a disaster when the potato crop failed." (2)  --Norman Rich, The Age of Nationalism and Reform, 1850-1890

Potatoes originally came from South America. They were
brought by Spanish explorers to Spain in the mid-16th
century. From there, the crop gradually spread throughout
Europe. 

Having had plenty of exposure to Polish cuisine and its heavy reliance on potatoes, I am curious to discover what Polish and other peasants of northern Europe ate before the arrival of the potato around 1600!