Vegetarianism is the theory an practice of the voluntarily nonconsumption of the flesh of any animal (including sea animals) with or without also eschewing other animal derivatives, such as dairy products or eggs. The earliest records of vegetarianism as a concept and practice amongst a significant number of people concern ancient India and the ancient Greek civilization in southern Italy and in Greece. In both instances the diet was closely connected with the idea of nonviolence towards animals (called ahimsa in India) and was promoted by religious groups and philosophers. Following the Christianization of the Roman Empire in late antiquity, vegetarianism practically disappeared from Europe. Several orders of monks in medieval Europe restricted or banned the consumption of meat for ascetic reasons, but none of them eschewed fish. So these monks were not vegetarians, but some of them were pescetarians. Vegetarianism was to reemerge somewhat in Europe during the Renaissance. It became a more widespread practice in the 19th and 20th centuries.