Beer is broadly defined as a fermented malt beverage. The word beer comes from the Latin word 'bibere' meaning 'to drink'. The Greek goddess of agriculture, Ceres, is the root of the Spanish word for beer, cerveza. One of the first great works of world literature, the Gilgamesh Epic, references the importance of beer. Beer has played an important role in the lives of many cultures throughout history, however it's impact on these societies is not widely known. High Schools don't teach "Beer History" classes. This is niche of history that while largely untaught is very interesting to people today, history buff or not. This is because roughly the same beverage that the Samarians brewed 6000 years ago still has an influential place in our society. I won't try to give the entire history of beer, the internet has given us encyclopedic references for that (see references), however I will give an outline for those not willing to read that much.

     The first civilized culture to brew beer was that of the Samarians in Mesopotamia. They called it a "Divine Drink" and offered it to their gods. The earliest record of beer is a 6000 year old Samarian tablet that depicted a group of people drinking from a communal bowl using reed straws. The Gilgamesh Epic likens the evolution from primitive man to "cultured man", to a man with and without beer:
     "...Enkidu knew not, what bread was nor how one ate it.
     He had also not learned to drink beer. The whore opened her mouth
     and spoke to Enkidu: 'Eat the bread now, O Enkidu, as it belongs
     to life. Drink also beer, as it is the custom of the land'..."

     The culture of the Babylonians derived from that of the Samarians and consequently developed the art of brewing beer. They developed the capability to brew 20 different kinds of beer. There is 4000 year old a clay tablet that depicts master brewers as highly respected members of society. These Babylonian master brewers were women as well as priestesses. The patronesses of beer were the goddesses Siris and Nimkasi and there were certain types of beer reserved exclusively for temple ceremonies. In 2100 BC Hammurabi, the 6th King of Babylonia, decreed the first written laws. Included in the laws was a daily beer ration based on the individuals established social standing. During this time, beer was never sold, it was used for trade. Hammurabi would order a saloon keeper drowned for accepting currency for beer.

     In Israel a tablet was uncovered that was 3000 years old. It indicated that beer was produced in Israel as early as the days of King Saul and King David. According to a 2000 year old Assyrian tablet, beer was brought aboard the Arc by Noah.

     There is a specific hieroglyph for "brewer"; this shows the importance of beer in the Egyptian culture. The Egyptians would gather in a "house of beer" in the evenings, it was an important part the diet of royalty and peasants alike. Beer was also used as a medicine. There is a medical document written in about 1600BC that includes about 700 prescriptions. About 100 of them contain beer. Beer was also offered as a gift to or to appease the gods. The nature goddess, Isis, was the patroness of Beer Brewing, therefore if was important that the beer be of good quality. Beer is also mentioned in the "Book of the Dead", and many Egyptian wall hangings.

     It is believed that the Egyptians taught the Greeks how to brew beer. Historians even suggest that the pre-historic beer god Dionysis is the root of the Greek wine god Dionysus. Beer was important to the Greeks, so much so that the famous writer Sophocles included beer as part of his suggested diet. The Greeks then taught the Romans how to brew beer, who in turn taught the savage tribes in Britain. However, once wine became more prevalent in Rome, beer was only brewed on the extreme outskirts of the empire, where one could not get wine. Because of this, beer became known as a drink of savages.

     From the Romans the art of brewing beer was spread to the Celtic and Teutonic peoples of Britain and central Europe. But beer did not regain its stature until the Christian monasteries began to brew and improve it. The monks built the first breweries that provided food, shelter, and drink to travelers, the start of the hotel industry. There are three Christian Saints that are considered the patrons of brewing; Saint Augustine of Hippo, author of the confessions; Saint Luke the Evangelist; and Saint Nicholas of Myra Santa Clause).

     In medieval times beer was brewed by women, as it was considered "food-drink". The women were also the cooks, and were known as "ale-wives". They would learn from the monks who had established the best methods of brewing beer. Many things around this time used the "ale". For instance brides would often sell ale to help pay for the wedding, hence the term "bride-ale", or "bridal". Also the expression "Yule-tide" derived from the expression "ale-tide". When the "Wayfarer Dole" was established, beer would be given for free to travelers. A pilgrim's dole can still be claimed today at the Hospital of St Cross, Winchester, England.

     Beer developed into what it is today through industrial revolutions and the continued progression of the same cultures that brought it through the medieval times.

References:
      http://en.wikipedia.org/wiki/History_of_beer
      http://www.fosters.com.au/enjoy/beer/history_of_beer.htm
      http://www.eat-online.net/english/habits/beer_in_ancient_times.htm