March 23, 2000
Researchers Trace Roots of Irish and Wind Up in
The Human Genome Project
New York Times on the Web: Science
Discussion on DNA Research
By NICHOLAS WADE
or any observer of last week's St. Patrick's
Day celebrators who wondered where all those Irish came from,
science has provided an unexpected answer: Spain.
Using ancient Irish surnames and DNA analysis, researchers
at Trinity College in Dublin have developed evidence that Irish
men in Connaught, a western province of Ireland, are almost all
descended from a population of hunters and gatherers who inhabited
Ireland before the invention of agriculture.
Archaeologists believe the inventors of agriculture migrated from
their homeland in the Near East, starting about 9,500 years ago, and
gradually spread across Europe, displacing the existing inhabitants or
intermarrying with them.
Dr. Daniel G. Bradley and colleagues at Trinity analyzed a DNA
signature that was assumed to belong to the first inhabitants. In
terms of the percentage of the population that carries the signature,
there is a gradient across Europe, from 2 percent in Turkey to 63
percent in Britain to 78 percent in Ireland as a whole, as if
reflecting the degree of mixing between Europe's ancestral hunters and
gatherers and the farming invaders from the east.
The signature, a set of variations in the usual DNA sequence, is
carried on the Y chromosome, which is bequeathed unchanged from father
to son. Since surnames are inherited the same way Y chromosomes are in
Ireland, Dr. Bradley measured the commonness of the DNA
signature in Irish men with surnames known to originate in the
north, south, east and west of Ireland.
He and his colleagues report in today's issue of the journal Nature
that the DNA signature gradient continues within Ireland, with
98 percent of Connaught men, on the west coast, carrying the
From genetic variations within the signature, Dr. Bradley estimates
the Irish versions of it stemmed from individuals who lived
4,000 or more years ago. Ireland is believed to have been
inhabited for 9,000 years, so Irish men who carry the signature
could well be descendants of their country's very first occupants.
"It seems that in our extreme west of Ireland we have a
snapshot of what western Europe was like before farming," Dr. Bradley
But where did those first hunter-gatherers come from?
The first carriers of the ancestral European DNA signature are
estimated to have lived some 30,000 years ago and presumably were
among the earliest modern human occupants of the continent after the
Neanderthals were driven out. Outside of Ireland, the signature
is most common in the Basque country of northern Spain, where 89
percent of men carry it.
In the last ice age, which lasted in Europe until around 10,000
years ago, Spain was a refuge for many plants and animals that
recolonized Europe as the glaciers retreated. Dr. Bradley believes
people may have done the same.
"They may have peopled this part of Europe by coming up from
Spain," he said.
Dr. Bryan Sykes, a human geneticist at the University of Oxford in
England, said he had traced a similar pattern of gene flow, from Spain
through Brittany, Ireland and the west of Scotland. People of
the Mesolithic period -- the Middle Stone Age -- were apparently
taking a sea route from southern Europe's warm refuges as the glaciers
The geneticists are not the first to link the Irish with
Spain. A Celtic legend says that the sons of a man named
Milesius arrived in Ireland from Spain 1,000 years before the
birth of Christ.