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Chromosomes Sketch New
Outline of British History
May 27, 2003
By NICHOLAS WADE
History books favor stories of conquest, not of continuity, so it is
perhaps not surprising that many Englishmen grow up believing they are a
fighting mixture of the Romans, Anglo-Saxons, Danes, Vikings and Normans
who invaded Britain. The defeated Celts, by this reckoning, left their
legacy only in the hinterlands of Ireland, Scotland and Wales.
A new genetic survey of Y
chromosomes throughout the British Isles has revealed a very different
story. The Celtic inhabitants of Britain were real survivors. Nowhere were
they entirely replaced by the invaders
and they survive in high proportions, often 50 percent or more, throughout
the British Isles, according to a study by Dr. Cristian Capelli, Dr. David
B. Goldstein and others at University College London.
The study, being reported
today in Current Biology, was based on comparing Y chromosomes sampled
throughout the British Isles with the invaders' Y chromosomes, as
represented by the present-day descendants of the Danes, Vikings (in
Norway) and Anglo-Saxons (in Schleswig-Holstein in northern Germany).
The survey began as a
request from the British Broadcasting Corporation to look for genetic
signatures of the Vikings in England, later broadened to include the Danes
and Anglo-Saxons. Dr. Goldstein said that not enough money was available
to study two other invaders, the Romans and the Normans, but that he felt
that their demographic contribution had probably been small.
He assumed the original
inhabitants of Britain could be represented by men living in Castlerea, in
central Ireland, a region not reached by any foreign invader. In a study
two years ago Dr. Goldstein and colleagues established that Y chromosomes
of Celtic populations were almost identical with those of the Basques.
The Basques live in a
mountainous refuge on the French-Spanish border and speak a language
wholly unrelated to the Indo-European tongues that swept into Europe some
8,000 years ago, bringing the agricultural revolution of the Neolithic
period. Hence they have long been regarded as likely remnants of the first
modern humans to reach Europe some 30,000 years ago, during the
Paleolithic.
By this chain of reasoning,
the Celtic-speaking men, since genetically very close to the Basques, must
also be drawn from the original Paleolithic inhabitants of Europe, and
probably represent the first modern human inhabitants of Britain who
settled the islands some 10,000 years ago, Dr. Goldstein said. These
original Britons must later have adopted from Europe both the Celtic
culture, evidence of which appears from some 3,000 years ago, and the
Celtic language, which is a branch of the Indo-European language family.
Having identified Y
chromosomes assumed typical of the original Britons, Dr. Goldstein and his
team could assess the demographic impact of the invaders. They found that
the Vikings left a heavy genetic imprint in the Orkneys, the islands off
the northeast coast of Scotland, which were a center of Viking operations
between A.D. 800 and 1200. Many men in York and east England carry Danish
Y chromosomes. But surprisingly, there is little sign of Anglo-Saxon
heritage in southern England.
"One tends to think of
England as Anglo-Saxon," Dr. Goldstein said. "But we show quite clearly
there was not complete replacement of existing populations by either
Anglo-Saxons or Danes. It looks like the Celts did hold out."
The Y chromosome measures
only the activities of men. In a survey reported two years ago, Dr.
Goldstein and colleagues examined British mitochondrial DNA, a genetic
element inherited through the mother. Surprisingly, the British maternal
heritage turned out to be more like that of northern Europeans than
British Y chromosomes are.
To explain that finding, it
is not necessary to assume Britain was invaded by an army of Amazons, Dr.
Goldstein said, or that the Celts had suddenly decided to replace their
Celtic wives with women from the Middle East. More probably, since Celts
in Britain remained in contact with those in Europe, there were continual
exchanges that included women. As in many cultures, the Celtic men stayed
put while women moved to their husbands' villages.
So over time, Britain's
female population would gradually have become more like that of Northern
Europe, Dr. Goldstein suggested.
British historians have
generally emphasized the Roman and Anglo-Saxon contributions to English
culture at the expense of the Celtic. A recent history of Britain, "The
Isles" by Norman Davies, tried to redress the balance. The Celts were
ignored, he noted, in part because no documentary histories remain, the
Celts having regarded writing as a threat to their oral traditions.
Generations of historians saw British history as beginning with Roman
invasions of the first century A.D. and indeed identified with
the Romans rather than the defeated Celts.
"So long as classical
education and classical prejudices prevailed, educated Englishmen
inevitably saw
ancient Britain as an alien land," Dr. Davies writes. The new survey
indicates that the genetic contribution of the Celts has been as much
underestimated as their historical legacy.
Dr. Davies said in an
interview that "traditionally, historians thought in terms of invasions:
the Celts took
over the islands, then the Romans, then the Anglo-Saxons."
"It now seems much more
likely that the resident population doesn't change as much as thought," he
continued. "The people stay put but are reculturalized by some new
dominant culture."
The Y chromosome is a
useful way of tracking men because it is passed unchanged from father to
son, escaping the genetic shuffle between generations that affects the
rest of the genome. Also, all men carry the same Y chromosome, a
surprising situation derived from the fact that in the ancestral human
population some men had no children or only daughters, so that in each
generation some Y chromosomes disappeared until only one was left.
This one and only Y has the
same sequence of DNA units in every man alive except for the occasional
mutation that has cropped up every thousand years or so and is then
inherited by all that individuals' descendants. Geneticists can draw up
family trees based on these mutations as branching points and then assign
specific lineages to historic events or locations, like the entry of
Neolithic farmers into Europe. |
