The Ball is round

Through out history, humans have enjoyed kicking a ball or something like a ball. South American Indians were known to use a light elasticized ball. However; rubber was not to be practically manufactured until a few thousand years later.

According to historical references and legend, early balls ranged from human heads, stitched up cloth, animal and human skulls to pig or cow bladders.

During the Ts'in and Han Dynasties (255 BC-220 AD), the Chinese played 'tsu chu', in which animal-skin balls were dribbled through gaps in a net stretched between two poles. Certain ancient Egyptian rites are said by historians to have similarities with football, and both the ancient Greeks and Romans also played a game that entailed carrying and kicking a ball.

According to pre-medieval legend, an entire village would kick a skull along a path to a nearby village square. The opposing village would in turn attempt to kick the skull to the first village's square. Wow, that probably caused more riots than in modern soccer games.

A Medieval custom was to take pig bladders used from live stock killed in preparation for winter sustenance and inflate them. They would play a game using their feet and hands to keep the "ball" in the air. Sounds like hacky sack to me.

The animal bladder balls were eventually covered with leather for better shape retention.