Blood. Blood Groups

The opening of the twentieth century saw a serological victory of a rather unexpected type. It dealt not with disease but with individual differences in human blood.

Physicians throughout history had occasionally tried to make up the blood loss in extensive hemorrhage by transferring blood from a healthy man, or even from an animal, into the veins of a patient. Despite occasional success, death was often hastened by such treatment, and most European nations had, by the end of the nineteenth century, prohibited attempts at such blood transfusions.

The Austrian physician, Karl Landsteiner (1868-1943), found the key to the problem. He discovered, in 1900, that human blood differed in the capacity of serum to agglutinate red blood corpuscles (that is, to cause them to clump together). One sample of blood serum might clump red blood corpuscles from person A but not from person B. Another sample of serum might, in reverse, clump the corpuscles from person B but not from person A. Still another sample might clump both, and yet another might clump neither. By 1902, Landsteiner had clearly divided human blood into four "blood groups" or "blood types" which he named A, B, AB, and O.

Once this was done, it was a simple task to show that in certain combinations, transfusion was safe; while in others, the incoming red cells would be agglutinated, with possibly fatal results. Blood transfusion, based on a careful foreknowledge of blood groups of both patient and donor, became an important adjunct to medical practice at once.

Over the next forty years, Landsteiner and others discovered additional blood groups which did not affect transfusion. However, all these blood groups were inherited according to the Mendelian laws of inheritance (as was first shown in 1910) and they now form the basis for "paternity tests." Thus, two parents both of blood type A cannot have a child of blood type B, and such a child has either been switched in the hospital or has a father other than the suspected one.

Blood groups have come to offer a reasonable solution, too, for the age-old problem of "race." Men have always divided other men into groups, usually on some subjective and emotional basis that left their own group "superior." Even now, the layman tends to divide humanity into races on the basis of skin color.

The manner in which differences among individual human beings are gradual and not sharp, a matter of degree rather than of kind, was first made clear by a Belgian astronomer, Lambert Adolphe Jacques Quetelet (1796-1874). He applied statistical methods to the study of human beings and may therefore be considered a founder of anthropology (the study of the natural history of man).

He recorded the chest measurements of Scottish soldiers, the height of French Army draftees, and other such items and, by 1835, found that these varied from the average in the same manner that one would expect of the fall of dice or of the scatter of bullet holes about a bull's eye. In this way, randomness invaded the human realm and, in one more way, life was shown to follow the same laws that governed the inanimate universe.

A Swedish anatomist, Anders Adolf Retzius (1796-1860), tried to bend such anthropological measurements to the problem of race. The ratio of skull width to skull length, multiplied by 100, he called the "cranial index." A cranial index of less than 80 was "dolichocephalic" (long head) while one of over 80 was "brachycephalic" (wide head). In this way, Europeans could be divided into "Nordics" (tall and dolichocephalic); "Mediterranean’s" (short and dolichocephalic), and "Alpines" (short and brachycephalic).

This is not really as satisfactory as it seems, for the differences are small, they do not apply well outside Europe and, finally, the cranial index is not really fixed and inborn but can be altered by vitamin deficiencies and by the environment to which the infant is subjected.

Once blood groups were discovered, however, the possibility of using these for classification proved attractive. For one thing, they are not a visible characteristic and therefore can't be used as a handy index for racism. They are truly inbom and are not affected by environment, and they are mixed freely down the generations since men and women are not influenced in the choice of mates by any consideration of blood groups (as they might be by visible characteristics).

No one blood group can be used to distinguish one race from another, but the average distributions of all the blood groups become significant when large numbers are compared. A leader in this branch of anthropology is the American immunologist, William Clouser Boyd (1903- ). During the 1930s, he and his wife traveled to various parts of the earth, blood-typing the populations. From the data so obtained and from similar data obtained from others, Boyd, in 1956, was able to divide the human species into thirteen groups.

Most of these followed logical geographic divisions. A surprise, however, was the existence of an "Early European" race characterized by the presence of unusually high frequencies of a blood group termed "Rh minus." The Early Europeans were largely displaced by modern Europeans but a remnant (the Basques) persist even yet in the mountain fastness’s of the western Pyrenees.

Blood group frequencies can also be used to trace the course of prehistoric migrations, or even some that are not prehistoric. For instance, the percentage of blood type B is highest among the inhabitants of central Asia and falls off as one progresses westward and eastward. That it occurs at all in western Europe is thought by some to be the result of the periodic invasions of Europe during ancient and medieval times by central Asian nomads such as the Huns and Mongols.