[Geographical hematology and population dynamics].
Hemotypology, which is based on the study of a large number of immunological and enzyme systems in the blood, has shown the extraordinary polymorphism of the human species and the lack of a genetic barrier between groups once considered as separate races. The typological mode of thought predominated in anthropology until the middle of this century. Mankind was divided into races according to a theoretical profile characteristic of each one, the holotype, which all the members of the same race were thought to resemble. Today we tend toward the substitution of population thinking: the human species, like all the other animal or plant species, is made up of populations, reproductive units whose members are more likely to mate within the group than outside it. A population is never totally closed and it is the interpopulational genetic flux which assures the homogeneity of the species. Three factors play a fundamental role in the genetic structure of human populations: 1. An ancestral genetic heritage from the distant past is modified by external contribution such as genetic flux and hybridization; 2. Chance is an especially important factor in very isolated small groups; 3. Natural selection: the majority of all genetic factors are not neutral, as we used to think, but possess a certain selective value. This nonneutrality doubtless explains the maintenance of the hemotypological polymorphism in man, as in the model proposed by A.E. Mourant and J. Ruffié. Following these ideas, sometimes it is possible to find the hemotypological traces of important events, especially of the great migrations of the beginning of the neolithic or the beginning of the historic period. Examples are cited which concern the peopling of sub-Saharan Africa, the western Mediterranean and western Europe, and of the continental Far East and Japan. This conceptual revolution, based on the dynamic idea of populations and not on that of the typological conception of race, has shed new light on the science of anthropology and has bridged the gap between hematology and history.