MONOGENISTS, the term applied to those anthropologists who claim that all mankind is descended from one original stock (ploos, single, and 7b,os, race), and even from a single pair; while polygenists (iroXbs, many) contend for a multiple ancestry. Aristotle and Vitruvius saw in climate and environment the natural cause of racial differences, influences far slighter in amount and slower in operation than was supposed. But although the reality of some such modification is not disputed, a remarkable permanence of type is dis played by races long after migration to climates extremely different from that of their former homes. Physically different races, such as the Bushmen and the pure negroid types in Africa, show no signs of approximation under the influence of the same climate; while the coast tribes of Tierra del Fuego and forest tribes of tropical Brazil continue to resemble each other, in spite of extreme differences of climate and food. Darwin is moderate in his estimation of the changes pro duced on races of man by climate and mode of life within the range of history (Descent of Man, pt. i. chs. 4 and 7). A great
difficulty of the monogenist theory lay in the shortness of the chronology with which it was formerly associated. It is now recognized (see MAN, EVOLUTION OF) that man has existed during a vast period of time.
A. R. Wallace suggested that the remotely ancient representa tives of the human race were in their wild state much more plastic than now to external nature. (Contributions to the Theory of Natural Selection, p. 319.) The polygenist theory is not dead. An interesting problem is raised by the discovery that the composition of the blood is trans mitted on Mendelian principles, and that there are at least two main varieties of blood. Further advances in physiology may help towards a solution of the question. The multiplicity of languages has been cited as evidence of polygenesis, but language is a social factor—part of the cultural acquisition of mankind—and efforts have been made to prove the common descent of all languages though links are missing and the data allow of other explanations.