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shared a recent common ancestry. However, when you factor in the results of the other blood
groups, the relationship becomes far more reasonable. The native Australians might have the same
proportions of the ABO blood groups, but the composition of the other groups, like Rhesus, MNS
and Duffy, are utterly different. Bit by bit, blood groups began to draw out connections between the
different peoples of the world, including western Europeans and the people of the Isles.
The basic pattern which Mourant found across western Europe, the area of most relevance for
Blood of the Isles, showed that across the whole region west of the River Elbe in Germany, group
A is high and group B comparatively low. East of the Elbe the opposite is the case. There is a
gradual shift from B to A, a so-called genetic cline, as we get closer to the Isles. In the Isles
themselves Mourant was able to call on absolutely vast amounts of material, both from his own
unit, by now incorporated as an official laboratory of the Medical Research Council, the UK’s
government funding agency for medical research, and from other published works. Among these
were detailed records of blood-group frequencies from Ireland, Wales and the Scottish Highlands.
Mourant gave the task of collecting all the records from the ‘missing’ bits – that is to say
England, lowland Scotland and Northern Ireland – to his long-term assistant Ada Kopec, who, with
a librarian and a secretary, made up the entire staff of the Blood Group Centre. It is plain from
reading the account of this mammoth piece of assimilation and statistical comparison of a grand
total of 477,806 results that Ada Kopec was far more concerned with mathematical manipulation of
the figures than with explanation. Indeed it is left to Mourant himself, writing in the Foreword,
almost to excuse his assistant from any genetic or anthropological interpretation, which, he writes,
‘will have to be made by others’. Fortunately, there were ‘others’ prepared to stick their necks out.
The conclusions of Mourant and Kopec’s gigantic enterprise can be summarized very
concisely. In Ireland there are very high levels of blood group O, the highest in Europe. The further
west you go, the higher the group O proportions. And, as elsewhere in Europe, where O is high, A
is low and vice versa, so in the eastern counties of Ireland, where O is lower than in the west, A is
higher. The differences in different parts of Ireland are not dramatic, but because the number of
individuals taking part is so high, the figures can be relied upon to be statistically reliable. So
whereas in County Clare, in the far west of Ireland, 80 per cent of people are in group O, this
drops to 73 per cent in County Wexford in the south-east, with a mirror-image result for blood
group A. Turning to blood group B, there is a slight reversal of the trend across the rest of northwest
Europe. Instead of following the rule of the further west, the lower the proportion of B, there
is a distinct and statistically significant rise in the far west of Ireland compared to the east. It goes
from 6.6 per cent in Wexford to 8 per cent in Kerry.
Now comes the explanation. According to Professor Geoffrey Dawson from Trinity College
Dublin, the high levels of A in south-east Ireland are a direct result of successive waves of
immigration into Ireland from England. In the first of many papers on the blood groups of Ireland,
written in the 1950s, Dawson kicks off with a summary history of Ireland. He explains the bloodgroup
changes from east to west by the Anglo-Norman invasion in the twelfth century, which we
will revisit in a later chapter, and by attempts to settle English immigrants under Queens Mary and
Elizabeth in the late 1500s.
I much prefer it when authors do advance a theory to explain their results, rather than leave it to
others. But how can Dawson possibly know this is the reason for the blood-group differences?
Why could they not be equally well explained by other movements of people in prehistoric times?