204 APPENDIX II INTENSIVE SEGREGATION. 



with the exception of a few of mankind, and still fewer of domestic 

 animals, it may be truly said of every individual mammal that all its 

 ancestry, through all generations since they became fairly mammalian, 

 have had this instinct in full force ; and yet it sometimes fails and the 

 line of descent is cut short with the individual that fails. Till compara- 

 tively recent times the same was true of man ; but we now find some 

 cases in which the young survive in spite of their inability to suck, 

 and the constancy of this mammalian characteristic is being gradually 

 impaired. There is also in some races an increasing tendency to 

 shorter periods of lactation, of to the entire suppression of the func- 

 tion; so that it seems not improbable that there may yet arise a 

 variety of the human species in which the power will be comparatively 

 obsolete. Under such conditions the instinct for sucking would cease 

 to be of any advantage, while special advantage would accrue to those 

 best able to thrive on the artificial food habitually provided by the 

 parents. In some countries this would be the milk of ruminating 

 animals, while in other countries it would be some vegetable prepara- 

 tion. Through this diversity in the food provided by the parents for 

 their infants and small children, there is even now a constant diversity 

 in the parental selection prevailing in different countries. Diversity 

 in the forms of parental selection is also produced by diversity in the 

 clothing and artificial heat provided by parents; in the protection, on 

 the one hand, of children from the wind and rain and direct rays of the 

 sun, and on the other hand, their exposure to the same with shaven 

 heads or naked bodies ; and in the methods of binding, cramping, and 

 mutilating the head, feet, waist, and other parts of the body. From 

 this point of view we see how largely the form of parental selection is 

 determined by social custom, and how it is sometimes enforced by 

 social selection, which excludes from the benefits of the caste or tribe 

 all who have not passed through the ordeal. 



As filio-parental selection is due to different degrees of adaptation 

 between the parent and offspring, it may be characterized not only by 

 fatal departures in offspring from the characters required in their rela- 

 tions to their parents, but by fatal departures in parents from the char- 

 acters required in parents in their relations to their offspring. As an 

 example of the former, we may refer to the death at birth of children 

 with excessively large heads ; and as an example of the latter, to the 

 death at birth of all the children of a mother with a contracted pelvis. 



(13) Dominational selection. Variations that are equally fitted to 

 cope with the environment may be divided into two classes those 

 better able and those less able to cope with other members of the 

 species in the appropriation of resources. Increase of population and 



