Thousands of years ago there were no numbers to represent one, two, or three. Instead, people used fingers, rocks, sticks, or eyes to represent numbers. There were neither clocks nor calendars to help keep track of time. The Sun and the Moon were used to distinguish between 1:00 P.M. and 4:00 P.M. Most civilizations did not have words for numbers larger than two so they used terminology familiar to them such as flocks of sheep, heaps of grain, piles of sticks or stones, or groups of people. People had little need for a numeric system until they formed clans, villages, and settlements and began a system of bartering and trade that in turn created a demand for currency. The Babylonians, who lived in Mesopotamia, between the Tigris and Euphrates rivers, began a numbering system about 5,000 years ago. It is one of the oldest numbering systems in the world. The ancient Egyptians used special symbols, known as pictographs, to write down numbers more than 3,000 years ago. The Babylonians and the Egyptians were the first to complete a system for arithmetic based on whole numbers and positive rational numbers. About 500 B.C.E. the Romans developed a system of numerals that used letters from their alphabet rather than special symbols (for example, III represented three). Roman Numerals was the standard numbering system and method of arithmetic in ancient Rome and Europe until about 900 C.E., when the Arabic numbering system, which was originated by the Hindus, came into use. Today, we use numbers based on the Hindu-Arabic system. We can write down any number using combinations of up to 10 different symbols (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9).