928 



SCIENCE. 



[N. S. Vol. XV. No. 389. 



progress. The truth lies rather with the 

 contrary proposition, since the unknown 

 causes of variation also predispose to the 

 perpetuation, communication and accumu- 

 lation of organic, physiologic and other 

 tendencies of change. Some variations or 

 mutations are of little evolutionary signifi- 

 cance and must be segregated in order to 

 be preserved, but others are notably pre- 

 potent and are accepted by a large propor- 

 tion of the individuals of successive gener- 

 ations. Reproductive accessibility to pre- 

 potent variations is the measure of evolu- 

 tionary progress. Species confined to small 

 areas are often distinct from each other by 

 characters of no diagnostic significance 

 among related forms of wide distribution. 

 The latter appear plastic and flexible be- 

 cause they have access to many avenues 

 of biological motion, while the former 

 maintain a relatively nan-ow and stable 

 uniformity because the few genetic varia- 

 tions are soon distributed through the small 

 number of individuals. 



Evolution may be termed a kinetic* pro- 

 cess because change is not only a potential 

 but an essential of organic existence. 

 Static theories have sought to explain or- 

 ganic changes as the results of external 

 influences; dynamic theories imply the 

 organic predetermination of such changes; 

 only under a kinetic theory may we admit 

 that the changes of biological evolution 

 have not been caused by external condi- 

 tions nor by internal mechanisms, but are 

 the manifestations of a form of motion the 

 nature and efficient causes of which are 

 even farther beyond the present range of 

 our comprehension than those of the mo- 

 tions which underlie the phenomena of 

 physics and chemistry. 



Plowever striking their results in partic- 

 ular instances, natural and other forms of 

 selection represent the incidents rather 



* ' A Kinetic Theory of Evolution,' Science, 

 N. S., Vol. 13, June 21, 1901, p. 969. 



than the causes of evolution, and instead 

 of being called forth and carried forward 

 only by external forces, the gradual accen- 

 tuation of characters of no direct impor- 

 tance or utility commonly accompanies 

 increasing organic efficiency. Thus it has 

 been found that varietal divergences from 

 the specific mean of the human skull are 

 correlated with increased intellectual 

 power, as represented by greater cerebral 

 bulk. 



"In a brachycephalie race the rounder 

 the skull the greater the capacity, in a 

 dolichocephalic race the narrower the skull 

 the greater the capaeity^the greater ca- 

 pacity following the emphasis of the racial 

 character."* 



Equally indifferent functionally and 

 selectively are most of the characters of 

 skin, hair, bones and other physical fea- 

 tures used by anthropologists in classify- 

 ing mankind, and in speculating upon the 

 origins of the various ethnic groups. 

 Closely analogous differences are found 

 everywhere among the species and varie- 

 ties of mammals, and they require no spe- 

 cial explanation unless it be to place them 

 among the many indications that the va- 

 rieties of primitive man had fewer facili- 

 ties of transportation and more definite 

 geographical localization than their mod- 

 ern representatives. Had such segrega- 

 tion become complete all the requirements 

 for the differentiation of species would 

 have been met, and modern zoologists 

 could make no serious or consistent objec- 

 tion to the treatment of the Tasmanians, 

 Australians, Andamanese, Papuans, Ainust 

 and similarly isolated groups as species, 

 no matter how insignificant a fraction of 



* Alice Lee in Science, N. S., Vol. 12, No. 312, 

 p. 948. 



f I am indebted to Dr. Leonhard Stejneger for 

 the suggestion of racial affinity between the 

 Papuans and Ainus. Dr. Stejneger holds also that 

 the domestic and social economy of the Ainus indi- 

 cates tropical origin. 



