258 THE STATUS OF MAN. 



typical Mongolian and a typical Malay. How about the Jap- 

 anese, is the population of Japan a variety of the Mongolian 

 species or a variety of the Malay species? In dogs we may con- 

 ceive of a typical hound and a typical terrier, two species. Is 

 the Dachshund a variety of the hound or a variety of the 

 terrier-species? Does not this classification of domestic dogs 

 exist simply to admit of dividing a book on dogs in chapters in 

 a convenient way? Is not the same true in mankind? 



What keeps species different ? All those causes which make 

 the number of matings between members of one species suffic- 

 iently more frequent than matings between members of dif- 

 ferent species. And it obviously depends upon the factors 

 which reduce the potential variability of a group, how much 

 inter-crossing is constisent with specific diversity. 



To take a concrete instance, why are the Airedale- terrier and 

 the Grey-hound separate species? What keeps them separate? 

 We know that hybrids are perfectly fertile, and that there is 

 no preferential mating in these dogs. We find that most dog- 

 owners keep males, and that the females are mostly owned by 

 breeders. These owners of the females guard the mating of 

 their animals, so that almost every puppy raised from either 

 an Airedale or a Grey-hound mother is sired by a male of the 

 same species. There is no inter-breeding worth the name be- 

 tween these two groups, hybrid females have a poor chance of 

 being allowed to grow up. Pure Airedales have their value for 

 certain definite purposes and a mating between two Airedales 

 will produce dogs that fit certain requirements. The same is 

 true of purebred Grey-hounds, the hybrids on the contrary 

 have an uncertain value, they are not wanted. 



We could give several instances where wild species coexist 

 in one locality, which give perfectly fertile hybrids, in those 

 cases where the two happen to fit into somewhat different 

 ecological niches. The reason we choose the example of the 

 dogs is to show, how in this matter of the remaining distinct of 

 species, we are concerned with the relation between causes 

 reducing the potential variability as opposed to frequency of 



