The Diego Blood Group System and the Mongoloid Realm (review)

The Diego Blood Group System and the Mongoloid Realm, by Miguel Layrisse and Johannes Wilbert. Caracas, Venezuela: Fundación La Salle de Ciencias Naturales and Instituto Caribe de Antropología y Sociología. 1999. 333 pp. No price given (orders through icas56@yahoo.com) (softcover).

The development of human population genetics over the last 100 years has closely paralleled the main theoretical and methodological advances that characterized Mendel's science. Significant breakthroughs were the discovery by L. and H. Hirzfeld in 1919 that the prevalences of the ABO blood groups varied in different ethnic groups, the development of starch gel electrophoresis by O. Smithies in 1955 (which led to the protein electrophoresis era), and the application of molecular techniques in the 1970s (which made possible the direct study of DNA variability). Superimposed on that was the progress in informatics, allowing the detailed analysis of huge amounts of data. It was also soon realized that for the correct interpretation of human genetic variability the contributions of archeology, paleoanthropology, linguistics, and social anthropology should also be considered.

It is within this context that we should consider this book, which synthesizes more then 40 years of interaction between the authors, a hematologist (M.L.) and an anthropologist (J.W.). Formally, this work is an updating of a monograph (El Antígeno del Sistema Diego, 1960, Caracas, Venezuela: Editorial Sucre) that they published 39 years ago. But it is much more than that, since they took the opportunity to thoroughly review the literature on human origins and diversification, with emphasis on Asian and Asian-derived populations.

The book is divided into seven chapters, which include the Diego blood group discovery and early research, a characterization of its antigens and antibodies, and an extensive and erudite discussion of its distribution. Its distribution is then compared with that of other protein and DNA markers, as well as with morphological, linguistic, and other anthropological evidence. No less than 537 surveys in 188 ethnic groups, comprising 90,644 blood specimens, were considered. The bibliography lists around 1000 references.

Everything started in 1953, when a woman from Caracas delivered her second baby, who later developed hemolytic jaundice. It was realized that this was due to an incompatibility between the blood of the mother and that of the child, samples of which were sent to Philip Levine in New York, who characterized the antigen as a new, private factor. The child, whose name was Diego, unfortunately died of erythroblastosis a few days after birth. However, a subsequent pregnancy of the mother provided Miguel Layrisse and Tulio Arends with the opportunity to conduct in-depth investigations of the serology and genetics of this factor, initiating an investigation that extends to the present.

The Diego blood group system is composed of two variants, Di^a and Di^b, which are caused by a single amino acid change determined by the SLC4A1 (Solute Carrier Family 4, Anion Exchanger Member 1) gene. Di^a arises from the substitution of leucine for proline at position 854 of the band 3 protein, at location 17q21-q22 in the chromosome. The already mentioned global survey indicated that Di^a is basically a marker of Asian ancestry, but not all Asians have the antigen. It is hypothesized that the mutation appeared in people living in eastern Central Asia during the last glacial maximum. Both Diego(a) negatives and positives colonized America, and an extensive examination of their putative descendants is given. Special attention is given to the high frequencies of Diego(a-) present in the areas of southern South America, lower Middle America/upper South America, and northwestern North America. Populations from these areas were considered remnants of a first wave of migrants, which was followed by a second wave composed of Diego(a+) carriers.

Despite minor faults (for instance, the word "genotypes" instead of "alleles" in Tables 4-14), this book provides a wealth of information about human variability, and as such deserves consideration by...