Destabilized and exhausted by the crusades, Mongol invasions, the Hundred Years war, and finally, as the climate cooled dramatically in the 15th century, the Black Death, which reduced populations by as much as fifty percent, European society was reborn as the remaining people increasingly were wage earners rather than serfs, and technology boomed, sparked by the lack of workers. The rediscovery of classical works led to a demand for new authoritative versions purged of errors made by copyists and translators over the centuries. Movable type printing permitted the diffusion of this knowledge to a vastly increased public. Physicians, particularly, based on the first century herbal of the Greco-Roman Dioscorides, realized that wild plants they used were much more numerous in type and different from his descriptions. As new multitudes of plants poured into Europe in the wake of voyages of exploration, herbals became increasingly realistic and complex and split between purely medical works and those of a more general botanical nature. This led to the development of precise and useful taxonomy finally leading to works of great evolutionary significance.