Sometimes it's better to let sleeping dogs lie -- as the fifth generation of the famous Irish brewing family of Arthur Guinness found out when DNA tests were carried out to determine the family origins.
Now the roots of Ireland's greatest family tree -- the great Guinness brewing dynasty -- have been exposed as sprouting from more humble beginnings than high-born aristocratic gaels, as was previously believed.
DNA tests were carried out on the family's male Y chromosome in Trinity College Dublin at the request of the Guinness family.
The analysis revealed that brewery founder Arthur Guinness's claim that he was a descendent of the Magennis chieftains of Iveagh, in Co Down, was wrong, and that the family sprang from the subsidiary McCartan clan, a far less eminent family.
The discovery takes a hammer to Arthur Guinness's reinvention of himself as a man who revived the fortunes of his aristocratic family.
The Guinness founder's act of social climbing is said to have come as a surprise to Patrick Guinness -- the five times great grandson of Arthur and father of the supermodel Jasmine Guinness -- who has recently written a biography on the St James's Gate brewer.
The book, entitled Arthur's Round: The Life And Times Of Brewing Legend Arthur Guinness, has publicised details of the tests for the first time and has detailed the life and times of the world's most famous brewery owner which, until now, has remained very much unknown.
The book explains that where Arthur's genuine ancestors, the McCartans, once lived is a small village called Guiness or Ginnies.
The name of which is derived from the Irish Gion Ais, meaning wedge-shaped ridge -- thus clarifying the roots of the famous surname.
However, the pretensions arose when Arthur Guinness married in 1761 and engraved a silver cup with the armorial bearings of the Magennises of Iveagh -- a lion, with the red hand of Ulster, and a boar.
Around 1794, he had a seal made that also bore the Magennis arms and his eldest son, Hosea, had the family's use of the Magennis arms properly authorised by the Ulster Herald in 1814.
The Guinness family is so widespread in England and Ireland and has so many titles that it is sometimes referred to as 'The Beerage'.