HUMAN RACIAL DIFFERENTIATION 181 



been in plenty. In some places, as in parts of New Guinea, where 

 war is nearly perpetual and inter-marriages between tribes 

 comparatively rare, the inhabitants of almost every district, like 

 the land shells of Samoa l display stable characters which clearly 

 differentiate them from their neighbours. Even in Great Britain 

 we have still these local races, as in the Yorkshire dales and High- 

 land glens. So surely as a human race separates into two or more 

 sections between which interbreeding is restricted, just so surely 

 does differentiation set in. The section that remains in the 

 ancestral environment continues comparatively stable ; the section 

 that migrates undergoes swifter but always continuous and steady 

 adaptive change. Evidently there has been no lack of such varia- 

 tions as contribute to stable differentiation. 



299. If, then, evolution is due solely to mutations, how does it 

 happen that no favourable human mutations have been noted 

 neither large observable mutations, nor those which render mating 

 physiologically sterile ? The latter certainly have not occurred, for 

 differentiated human races are perfectly fertile when crossed. 

 The former as certainly have not occurred ; for written human 

 history stretches into thousands of years, and men are fond of 

 recording wonders, and none of this kind have been recorded. 

 I think no mutationist, in face of this massive evidence, will 

 venture to uphold the thesis that human differentiation has resulted 

 from mutations. And, if not human differentiation, why the 

 differentiation of other natural species and varieties ? As I say, we 

 have no reason to suppose that heredity in the animal man 

 differs from heredity in lower animals and in plants. 



300. In a few speaking comparatively, a very few instances, 

 mutations, occurring chiefly in self-fertilized plants, have been 

 known to persist without artificial aid for several generations. 2 In 

 every such case the mutation has been comparatively unimportant 

 as regards the function of the part that has undergone change. A 

 leaf or a flower has altered its shape or colour or texture, a flower- 

 stem has grown longer or shorter, the wing of a butterfly has 

 grown darker, and so forth. But all organs are not on the surface 

 of the body ; their co-adaptations, therefore, are not always so few 

 and simple as those of leaves and flowers. Consider a mutation 



1 See 332. 



2 The only mutation, human or other, if mutation it can be called, known to 

 have been persistent under natural conditions for a considerable length of time, 

 of which I am aware, is the Hapsburg lip, an ungainly feature of the reigning 

 house of Austria. I imagine it would have disappeared long ago if the faces it 

 marred had not belonged to an inbred imperial family* 



