The main cause of the breakdown of medieval society in Europe was the Black Plague of the 1300s, a devastating illness that swept through Asia and Europe and may have killed as much as a third of the total population. This devastation wiped out entire towns, leaving many without family or leadership or work. It resulted in a huge labor shortage, as the agricultural economies of Europe needed a large amount of man-power to plant and harvest crops. This drove up wages for workers who had previously earned very little, expanding society past the traditional medieval classes of peasant and nobility. Additionally, it helped to increase the population of cities, which became the important centers for the Renaissance, beginning in about 1400.