EVOLUTION, GENETICS, ANTHROPOLOGY — MOURANT 505 



characters were either relatively insignificant, or pathological. It is 

 therefore not surprising that the statistical approach of the bio- 

 metricians seemed to mark a much more promising line of advance, 

 both in explainmg evolution as a whole and in classifying and explain- 

 ing the differences between human individuals and populations. 



To three genetical statisticians, Fisher and Haldane in Britain, and 

 Sewall Wright in America, is due the credit for the next major develop- 

 ment in biological thought, the explanation of natural selection in 

 terms of genetics. The most complete treatment of the subject is found 

 in Fisher's The Genetical Theory of Natural Selection (1930) which 

 is one of the most important works on biology to appear since The 

 Origin of S'pecies. Following the work done by Huxley in establish- 

 ing the validity of the theory of natural selection, Fisher took the 

 next logically essential step and showed, in terms of the by then 

 well-established mechanisms of heredity, how selection had operated. 

 In genetical language, Darwin and Huxley studied phenotypes; 

 Fisher, genes and genotypes. Fisher, indeed, showed that the "atomic" 

 nature of heredity was implicit in the work of Darwin: granted that 

 evolution by natural selection took place, he showed that it could 

 happen in no other way. 



There could now be no doubt that the external and measurable body 

 characters which provided the data of physical anthropology were 

 genetically determined; Fisher and Gray (1937) in a concise paper 

 brought together all that was known regarding the inheritance 

 of stature in man and interpreted it in terms of genetical theory. The 

 inheritance of these characters, however, did not prove readily 

 amenable to genetical analysis, and has not even now proved to be so. 

 Thus, while the object of physical anthropology was (and is) to isolate 

 the inherited components in the measurements, and to use them for 

 purposes of classification and the tracing of ancestral relationships, 

 the observational methods perforce remained exclusively those of direct 

 measurement, and the methods of statistical analysis to which the 

 measurements were subjected took no cognizance of genetical theory. 



The field was now clear, however, for the exploitation, largely 

 fostered by Fisher himself, of blood groups and other genetically rela- 

 tively simple characters as genetical, and ultimately as anthropological, 

 markers. 



Despite Huxley's efforts to give medical students a broad back- 

 ground of biological knowledge, medical research at the time of his 

 death remained divided into a number of very distinct compartments. 

 The highly active field of bacteriology and the investigation of the 

 response of animals and human beings to bacterial infection was 

 scarcely seen to have any connection with the great advances in biology 

 initiated by Darwin and Huxley. It was, however, in the course of 



