Humorist Steven Wright has asked, "What do you suppose George Washington did? If anybody asked to see his ID, did he just whip out a quarter?" But I think his uniform alone would have sufficed.
Somewhere in a circle of prehistoric cave folk, one tribe organized itself enough to... well... to be a tribe. And whatever the tribe did to get by, be it pick fruit or hunt mammoths, one tribesman proved to be better at it than any other and became the leader. So the tribe saw that they did better with this person in charge, and appointed him as such. But it wasn't enough to mill around asking "Who's in charge?" until somebody pointed at the leader and said "That guy." So they gave that guy something special to wear, signifying him as leader. Now tribesmen couldn't mill around asking "Who's in charge?" any more. They could see the leader, and he was telling them to get to work. The concept of the uniform was born.
Of course, the concept was extended to the people whom the leader led. Pretty soon, as different tribes met and mingles, tribesmen created their own uniform as a way to distinguish themselves one tribe from another. Thereafter, the leader would be the king, the great Kahuna, or whatever, and he would have his special unique uniform, to show that there was only one like him. This concept is still exhibited today, in everyone from corporate businessmen to Maori tribesmen to the Pope to Chicago street gang members.
Everyone but everyone wears uniforms, even the people who are anarchisticly protesting society by refusing to wear one. Youth movements such as Goths, Hip Hoppers, Emo Kids, Gang Bangers, and Punkers have specific styles of dress they wear to identify themselves with their culture: uniform. Protesting against the sordid slaughter of animals for food? Become a vegan then, but don't forget to run right out and have the word 'vegan' tattooed on your wrist like all vegans do. Uniform! Hey, look, there's somebody protesting capitalist consumerism! You can tell by his tie-dyed shirt, Levis jeans, Grateful Dead patches, Foster Grant sunglasses, and American flag bandanna. Whenever we intentionally alter our appearance to conform to the standards of a group, that's a uniform.
There are some few recorded attempts at uniform dress in antiquity, going beyond the similarity to be expected of that nation's ethnic or that race's tribal dress. One example is the Spanish infantry of Hannibal, whose troops wore white tunics with crimson edgings. Another is the Spartan hoplite soldier in his red garment. The terracotta army discovered in the tomb of the first Emperor of Chin, circa 200 BC, have a distinct similarity as well as seven different styles of armor within that army's style, indicating a possible rank system.
The legions of the Roman Empire wore fairly standardized dress and armor. However, the concept of uniforms was not a significant part of their culture and there were considerable differences in details. Even the armor which was mass-produced in state factories varied according to the province of origin, showing the trademark of armorers rather than a standard of the army. Nevertheless, fragments of surviving clothing and wall paintings indicate that the basic tunic of the Roman soldier was of red wool; senior commanders are known to have worn white cloaks and plumes in their helmets. The centurions who made up the long-serving backbone of the legions were distinguished by traverse crests on their helmets, chest ornaments corresponding to our modern idea of medals and the long cudgels that they carried.
Uniform design must take into account the unified appearance of the group or organization and the different ranks, classes, and grades within that group. Thus, uniforms start out with a standard design, which is then augmented with additional decoration to designate someone of graduating rank or specialty.
The regular provincial and central troops of the East Roman Byzantine Empire are the first known soldiers to have had what would now be considered regimental or unit identification. During the tenth century AD, each of the cavalry bands making up these forces is recorded as having had plumes and other distinctions in a distinctive color. While some auxiliary cohorts in the late Roman period did also carry shields with distinctive colors or designs, there is no evidence that any one Roman legion was distinguished from another by features other than the numbers on the leather covers protecting their shields.
The feudal system of Western Europe provided instances of distinguishing features denoting allegiance to one or another lord. These, however, seldom went beyond crude colors and patterns painted on shields or embroidered on their coats. Orders of military monks such as the Knights Templar wore mantles respectively of white with red crosses on the shoulder or of black with white crosses over the usual pattern of armor for their periods.
The organized armies of the Ottoman Empire employed highly distinctive features of dress to distinguish one corps or class of soldier from another. An example would be the black, conical, felt hats worn by the Deli cavalry of the early nineteenth century. However, rather than distinguishing the grade or rank of the unit, the basic costume was usually that of the tribal group or social class from which a particular class of warrior was drawn. As such it was sufficiently varied not to rank as a uniform variation in the later sense. An elaborate system of colorful standards largely provided unit identification instead. It was not until the reorganization of the Ottoman Army by Sultan Mahmud II during the seventeenth century that completely standardized dress was issued.
Today's society employs many uniform standard strategies throughout groups affiliated by nation, military, business enterprise, trade, and group. When we informally declare a dress code, we are setting a loose kind of uniform within a business or school environment, specifically to standardize a set of rules and values reflected by the organization. Perhaps someday thousands of year from now, archaeologists will pull the scraps of our business attire from the rubble and attempt to guess what sort of folk we were. Whatever their conclusion, they will know that the concept of uniforms are an inevitable trapping of any organized society.