If being Jewish were in the blood, then what better way to find the markers of Jewishness then by studying blood itself? In his 1977 book
The Genetics of the Jews
, Arthur Mourant, one of the foremost cataloguers of blood groups during the 20th century, explained the advantages to this approach, “In popular anthropology since time immemorial…the visible and physically measurable body characteristics preceded the hereditary blood characteristics as the principal human taxonomic markers. Because of the precisely known mode of inheritance of blood characters, the latter have now superseded them… The hereditary diseases are, in general, too rare to be of value in studies of limited population samples…” So measuring blood groups is more precise than measuring heads and easier than identifying rare genetic diseases.
Mourant’s journey to Jewish population genetics was long. As an Oxford-trained geologist, he joined the Geological Survey of Great Britain during the 1920s to catalog the coal deposits in Lancashire. Unable to obtain an academic post in geology in Depression-era Britain, he returned to his native island of Jersey and set up a laboratory offering
medical tests. But running that laboratory was not satisfying, so in 1939, he entered St. Bartholomew’s Medical College in London. Upon his graduation with a medical degree in 1943, he became a Medical Officer in the National Blood Transfusion Service. The demand for blood products was great during the war and Mourant became a leader in the field.
After the war, he directed the UK Medical Research Council’s newly established Blood Group Reference Laboratory, the international standard for the World Health Organization.
A blood group is determined by the presence or absence of certain sugars, proteins, or fats on the surfaces of blood cells and other types of cells. Differences in blood groups limit the possibilities for blood transfusions — blood can be transfused only for a compatible type. Transfusions among individuals of noncompatible types result in transfusion reactions in which antibodies in the recipient’s blood break down the transfused red cells.