504 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



sisted almost exclusively of measurements of the various parts of 

 the body, and observations, with more or less precise measurements, 

 of the color of certain tissues. The total amount of information 

 amassed was prodigious. With the shift of stress from individual 

 to population, and the development of appropriate statistical methods 

 by Pearson, Fisher, and others, the material served to yield a fairly 

 complete classification of mankind, and to throw much light on 

 prehistory. 



Throughout the period which we are considering the underlying 

 object of investigators, even if it was not always expressed, was un- 

 doubtedly to define separately, and to measure, those features of the 

 bodily constitution which were inherited, as distinct from those ac- 

 quired during the life of the individual. But in the absence of any 

 adequate theory of the inheritance of these features the channels of 

 information tended in the course of time to become clogged by a vast 

 mass of rather indigestible data. 



GENETICS AND NATURAL SELECTION 



In 1900 two discoveries were announced which were to have a very 

 great influence on anthropology. One of these, and by far the more 

 important, was the rediscovery, independently by De Vries, by Cor- 

 rens, and by Tschermak, of those principles of genetics which had 

 already been described by Mendel in 1865 and which had been not 

 simply forgotten, but completely disregarded by the main body of 

 biologists. The other discovery, at first sight completely unrelated, 

 was that by Landsteiner of the human blood groups. 



The essence of the Mendelian revolution was the discovery that 

 the inherited characters, which taken together constitute the differ- 

 ences between individuals, are indeed separated from one another 

 by finite differences. In sexually reproducing species, any given 

 character results from the action of a pair of genes, one inherited 

 from the father and one from the mother or, perhaps more com- 

 monly, of several such pairs. When the individual reproduces, a 

 replica of one of each pair of genes is present in each of the reproduc- 

 tive cells and is passed on to each of the offspring. The further 

 discoveries that the genes are located on microscopically visible struc- 

 tures known as chromosomes, and that the latter consist chemically 

 of chains built up from desoxyribonucleic acid molecules, need not 

 concern us at present. 



It was not at first obvious that the new genetical theories were 

 relevant to the evolutionary process, to the theory of natural selection, 

 or to anthropology. The characters which were studied in the early 

 days of genetical science appeared to many biologists to be somewhat 

 superficial, and little connected with the great differences which 

 interested taxonomists. In man the few known genetically segregating 



