In the 18th and 19th century, the British living in India drank ale from England, largely because the Indian water supply caused digestive problems to humans not raised on it. Unfortunately, most beer could not survive the long journey from England to India in a hot ship's hold. From this problem, India Pale Ale (IPA) was born, brewed in Britain and designed (with high levels of alcohol and hops to act as a preservative) to withstand the long sea voyages of up to six months to distant parts of the British Empire like India.
In modern times, transportation problems have been solved and IPAs have evolved, usually with lower alcohol content than the traditional version, but still with significant levels of hops. Pale ales of today are still stronger than light ales and contain pronounced hop flavor and aroma with low to medium maltiness, a dry character, fruity esters, and a bitter quality.