After four years of research, which took them from Belgium to Bavaria to investigate ancient beer-making methods, archaeologists Declan Moore and Billy Quinn have found evidence of microbreweries across Ireland, which predates the 1759 foundation of the Guinness brewery by several thousand years.
The duo, part of the archaeological consultancy based in Co Galway has demonstrated that enigmatic man-made Bronze Age features, which are common throughout Ireland, are in fact ancient microbreweries.
The team has now recreated Bronze Age brewing methods and produced a modern version of the ale, which the ancient Celts would have drunk by the beaker after a hard day's hunting and gathering.
The research, which is to be published in Archaeology Ireland magazine next month, focuses on the 4,500 "fulacht fiadhs" (pits or recesses), which date from 1,500 BC and are dotted across the island nation.
The purpose of the horseshoe-shaped mounds surrounding an indentation has been a mystery since they were first identified in the 17th century.
In the 1950s it was proposed that they were filled with water, which was brought to the boil by adding heated stones and used to cook mutton. But a lack of animal bones around the sites led to Moore and Quinn to suggest an alternative use.
The duo believe large-scale beer drinking was carried out in Ireland long before the 6th century AD when brewing was first documented.
Studies of residues found at prehistoric sites in the Far East have dated beer back to 5,000 BC. But Moore and his colleagues claim the proliferation of fulacht fiadhs in Ireland suggests ancient brewing on an unprecedented scale.
"It means that there were up to 4,500 breweries in Ireland in the Bronze Age, which means it was the most widespread brewing industry in prehistory in the world," said Moore.
"We were not simply on a quest for beer. We were only interested in fulacht fiadhs and we were trying to find out what they were used for. It just so happens that they make an acceptable quality of beer," The Daily Telegraph quoted Quinn as saying.