Pre-history
The practice of removing hair from one's body traces its roots to well before the beginning of written history. Prehistoric cave drawings dating from as early as 30,000 B.C. show the earliest humans using clam shells and sharpened flint to (painfully, no doubt) remove hair from their bodies. Since that time shaving has enjoyed periods of great popularity and prominence as well as times of neglect and disfavor, depending on various cultural, technological, and political influences.
Early Razors
Between 30,000 B.C. and 6,000 B.C. razors evolved from clam shells and sharpened bits of flint and obsidian into somewhat more sophisticated instruments. Archeologists have discovered circular razors fashioned of bronze in ancient Egyptian burial chambers. The ancient Egyptians were known to shave their heads and faces, believing that hair was animalistic and uncivilized. By the fourth century B.C. the practice of shaving had spread to Greece and Rome, largely due to the influence of Alexander the Great. Alexander ordered his troops to shave their heads and faces in order to prevent their hair from being grabbed by enemies during battle. During this time the razor further evolved into elaborate instruments made of copper, iron, and even gold. It was under the development of the Greeks and Romans that the razor evolved from a curved implement into the more modern style of straight razor, a design that has persisted to the modern day.
Middle Ages
Throughout the Middle Ages, shaving came in and out of style based on the preferences of local lords and the religious climate of the time. In the eleventh century, the grooming industry began to flourish. Perfumes, deodorants, and other hygienic items became very popular, as did shaving. Much of this can be attributed to religious motivation. Following the 1054 split between the Eastern Orthodox church and the Roman Catholic church, western clergymen began advocating shaving as a way to distinguish themselves from their rivals in the east, as well as "infidels" such as Jews and Muslims. In 1096 the Archbishop of Rouen went so far as to outlaw the wearing of beards, with the exception of Crusaders and those traveling in the Holy Land, who were permitted to wear beards in deference to the example of the apostles.
Industrial Revolution
Except for occasional advances in metallurgical technology which made razors sharper and safer, there were few developments in razor design between the Middle Ages and the early Industrial Age. The early nineteenth century saw the development of the famous Sheffield straight razor, which resembles the straight razors used today. By this time, razors had become very precise, carefully crafted products. At this time, there was also a boom in the world of shaving-related cosmetics as many perfumers and chemists began to manufacture soaps and creams specifically designed to aid in the shaving process. Many of these companies are still in existence and continue to manufacture shaving products.