Early man had a lot of things to worry about, as our ancient ancestors were exposed to and relatively defenseless against ferocious predators like hyenas, cave bears, lions, wolves and saber-toothed cats. Another concern was dying of thirst, as man can only survive a few days without water. Living in groups made it necessary for man to devise ways to measure water because he was concerned about how much water he would be allowed to drink versus how much was given to the rest of the tribe. Early man must have learned how to share handfuls of water with the rest of the tribe and this was probably how primitive man first measured a defined volume of liquid. When early man was near a stream or lake and they got thirsty, they bent down and cupped their hands to drink water, and they stopped drinking when their thirst was met. Ancient man used animal skins for clothing and they learned that skins could be used to hold liquids. The first receptacles that were used for water drinking vessels were probably made from the hides of goats. This invention allowed early man to tote water with them when they journeyed away from their villages. Earthen ware drinking vessels eventually replaced skins for drawing and holding water, once man discovered the art of making pottery. Ancient people learned how to trade goods or services and this made it necessary for man to develop standards. Eventually standard size cups and bowls to hold water came as a result of this and that made it more convenient to drink, sell and trade according to liquid volume.