Soup experts believe that the delicious substance has existed since the development of pottery about 10,000 years ago. It has appeared in diets in prehistoric societies and in cultures on every inhabited continent around the world. A couple examples include Amazonian tribes who used turtle shells to boil their special version of turtle-entrail soup, and according to Greek historian Herodotus, the Scythians, who lived in Eurasia from approximately 800 to 400 B.C. and boiled animal flesh in water over bone fires.
Soups are a natural development in cookery for several reasons: They're easy to make, they can provide sustenance for large groups of people, the cooking process kills bacteria and parasites, they're easy to digest and they retain nutrients.
Soup is now distinguishable from stew with parameters put in place by the French around the 18th-century with the development and separation of broth and stock (and their refined forms, consommés, bouillon, purees and bisques) from potage, porridge and gruels. Potage simply denotes the contents of a pot, but also refers to the thick Medieval meat and vegetable soup, which was the primary (if not sole) element in peasant diets.
Porridge and gruel consist of grains and oats boiled in water to form a mushy cereal consistency like that of oatmeal or grits, though some consider gruel the product of boiling any starchy food, including legumes and root vegetables. Either way, under modern classifications, soups are characteristically thinner and have smaller pieces of meat and vegetables in them. They cook for a shorter period of time and typically accompany a meal. Stews, on the other hand, are thicker. They typically cook longer and are served as a main course.
Some classifications deem “soup” the umbrella term for a broad category, which includes stews, gruels or any liquid food. The word itself is derived from the Teutonic word suppa, which referred to a thick concoction poured onto bread, called sop. This morphed into the Old French word soupe, scaling down the vocabulary to encompass both the bread and the stew. Etymology and semantics aside, soup, or whatever you call it, with its voluminous variations, seems to originally be just solid foods boiled in water.