All gingers belong to one of two families. The largest and most diverse of these is Zingiberaceae, the scented ginger family. It consists of hundreds of species spread over more than 50 genera. All are perrenial herbs sprouting from tuberous rhizomes. Many species are popular ornamentals. Others are used as spices, processed for essential oils or employed for medicinal purposes. Amongst the ornamental varieties can be found ginger lilies (Hedychium spp.), shell gingers (Alpinia spp.) and torch gingers (Etlingera spp.). Spice gingers include melegueta pepper (Aframomum melegueta), Thai ginger (Alpinia galanga), the common or true gingers (Zingiber spp.), turmeric (Curcuma spp.) and cardamon (Amomum spp. and Elettaria spp.). 
Unscented gingers form the smaller spiral ginger family, Costaceae. This group consists of three genera, some species of which serve as ornamental or medicinal plants. Like their fragrant cousins, spiral gingers grow from a horizontally-creeping rhizome. The term "ginger family" is variously applied to both Zingiberaceae and also the order Zingiberales; which includes both ginger familes plus six others including Cannaceae and Musaceae. It is not difficult to see similarities between plants within this order. Musifolia or banana-like leaves are a common trait amongst Zingiberales species, as are starchy rhizomes with Arrowroot, the various ginger roots and Queensland arrowroot being edible examples. 
Spiral Ginger family
Copyright (c) 2008 Cary Bass
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Common Ginger (Zingiber spp.)
Common or true ginger does not grow in the wild and has been cultivated so long that its origins are uncertain. The centre of diversity seems to be India and the history points the same way. The Romans gained ginger from India over 2000 years ago and considered it a medicinal, rather than culinary plant. This is reflected in the name of the most common ginger, Zingiber officinale which means that it was sold in roman apothecaries. Arabs continued the supply to Europe over the centuries proceeding the fall of Rome, bringing ginger potted on ships from Asia. Culinary use of the herb appears in Indian literature from about the 5th century and became widespread by the advent of Mogul rule in the 13th century. By that time, the trade to Europe included preserved ginger which was used to make sweets. 
Demand for ginger in Europe increased over the medieval period as taste for it spread. The English in particular had a penchant for the herb. They managed to get it to the Carribean by the 16th century, where it was shortly being grown on a large scale. This was an important move as a discovery was about to follow that would bring Jamaican ginger to the fore.
Ginger Beer Plants
Around the middle of the 18th century, the first ginger beer plants appeared. These were used to brew an effervescent, alcoholic beverage that quickly earned wide popularity. This original or real ginger beer was quite different to anything commercially available today. It was cloudy, zesty and could contain as much as 11% alcohol by volume.  Only Jamaican ginger was used and the ginger beer plant or symbiotic combination of bacterium and yeast (SCOBY) originally employed, was bred from a specific mix of micro-organisms. In fact Harry Ward, a leading biologist of the time, collected and studied a large number of ginger beer plants (GBP), eventually declaring their constitutes new to science. He named the yeast Saccharomyces pyriformis (now named S. florentinus) and the bacterium Brevibacterium vermiforme (now named Lactobacillus hilgardii). 
By 1790 England was exporting ginger beer to Canada and the United States, which was made possible by the advent of pressure-sealed stoneware jars. It wasn't long however, before local breweries began to appear in both North American countries. About this, Donald Yates from the Federation of Historical Bottle Collectors, tells us ...
"Early Ginger Beer was produced locally in small quantities for use by taverns or families. Its popularity blossomed after the Civil War, when it was produced commercially in larger quantities, and transported to new markets. The most popular region for ginger beer was Western New York State, especially Syracuse and Buffalo. Ginger Beer breweries flourished along the Erie Canal due to convenient transportation and availability of raw materials for the stoneware and ginger beer. Ginger beer was brewed in smaller quantities in twenty other states." 
At the turn of 19th century, ginger beer was still being brewed using whole ginger, yeast & water. Honey, sugar or molasses was usually added as a sweetener and lemon juice was included in many recipes. An altenative made from ginger extract was developed around this time and named Ginger Ale. This beverage was clear and pungent, though by all reports, never achieved the character of real ginger beer. The popularity of ginger beer was still rising in England, Canada and the United States, leaving ginger ale to remain an inferior substitute for at least half a century.
In the 1850s, new English laws forced local ginger brewers to reduce the alcohol volume of their produce to 2%. Even watered-down, ginger beer remained popular, though ginger ale was gaining ground. This was even more the case in Canada, where ginger ale is probably still more popular than in any other country. Production of full strength ginger beer continued in the United States until the 1920s, when Prohibition brought it to a sudden end. This was at the height of the beverage's popularity, when more than 500 ginger breweries operated in the U.S. In Canada there were more than double that amount and in the UK, there were over 4000 breweries. 
The Modern Era
Prohibition triggered the age of soda pop in the United States. New soft drinks like Coca-Cola, root beer and carbonated ginger ales were quick to replace alcoholic beverages. In England, low strength ginger beer was still produced and sealed in stoneware until the 1940s. At that time, competition from glass bottling plants and the rising cost of pottery production finally brought the British love affair with the drink to a conclusion. Ginger beer had been the most popular alcoholic beverage in England for almost 200 years.
Real ginger beer has since faded into obscurity. Ginger ale remains widely available in soft drink form and a simple culture of ginger, sugar and water can be grown to produce a beverage often referred to as ginger beer. It was the specific use of both Jamaican ginger and the SCOBY described by Ward however, that gave real ginger beer its famously characteristic flavour and qualities.
Simple Culture Ginger Beer
In her article, "Ginger: Not Just for Men and Houses", Tina Bolin introduced us to common ginger and showed how to grow it. Just as your garden is potentially a healthy and economical source of ginger, brewing ginger beer or ale is a great way of using it. The easiest means of making ginger beer at home is using the simple culture method.
There are numerous recipes for this type of ginger beer that all involve growing a GBP or simple culture in a jar. The following recipe is reasonably close to the traditional method. An alternative here swaps the yeast for sultanas and another version here employs soda water (really as much a ginger ale as a beer). Other recipes include ingredients such as instant coffee, raw cane sugar, palm sugar and honey. It is fun to experiment with ginger beer and produce different flavours. Increasing the amount of sugar in the bottling syrup is not a good idea however, as it may result in exploding bottles.
The original 19th century ginger ale eventually became known as Golden Ginger Ale. It is quite obscure now and produced only by a handful of soft drink makers. Dry Ginger Ale is a paler, less distinctly-flavoured version that was developed and gained popularity as a mixer during Prohibition. The differences between ginger ale and ginger beer in the modern context, are really no greater than the variations within recipes for each of these beverages themselves. In historical terms, the difference is that ginger ale is normally non-alcoholic as it is not fermented with the same SCOBY as real ginger beer.
There are recipes for ginger ale here, here and here that all use soda water. Another recipe here describes a method of brewing the ale in the bottle using yeast. Again, the boundary between ale and beer is unclear. Names aside, the advantage of soda recipes over fermentation is time. That is, about half an hour compared to around a week.
Real Ginger Beer
Though it is practically a historical curiousity, real ginger beer is still made. There is a Yahoo Group listed below dedicated to brewing and sharing the original SCOBY. Members can find information about the traditional GBP, recipes and people experienced at making this antique drop. It is possible to make real ginger beer independently, though this entails finding an appropriate yeast supplier. There are yeast bank kits available and sites such as HomeBrewTalk that feature information about making frozen yeast banks at home.
From growing your own ginger through to harvesting it, brewing and enjoying the final result, making ginger beer or ale is entertaining and rewarding. The benefits of ginger in terms of health and nutrition have been recognised for thousands of years, so including it in your diet one way or another is never a bad idea. For kids especially, ginger beer is a better than soft drinks; with a choice of recipes ranging from quickly-made ales through to traditional fermentation, there are options for the busiest parent to the most experimental enthusiast. More than anything however, ginger beer plain tastes good as anyone who brews their own will agree.