The Persians, based in what is now Iran, ruled an empire in the 6th century BC that included most of the Middle East and Egypt. They introduced two garments to the history of clothing: trousers and seamed fitted coats, both probably first made from animal skins. These tailored garments differed significantly from the woven rectangles of cloth generally worn in the Mediterranean region, and they served to protect people from cold weather. They were adopted for that purpose by peoples of Central Asia and northern Europe. People who rode horses valued trousers for use when astride, and in that capacity trousers spread to China and India, as well as to the Celtic peoples of northern Europe.
It is worth noting that throughout most of history trousers have not been associated with men. In China, both men and women, especially those who worked the land, wore trousers. In the Ottoman Empire (based in what is now Turkey), women wore trousers. Only in European cultures did trousers become associated with men.