181 



Intergeneraut Offspring 



Groups. Groups. 



1st generation ... a 4- b produces a or f \ n „ 



c + d " e " h f 2nd Se™™*™- 



2nd generation ... e -\- f " c " b ) , 



^ + h « a » <* ) 3rd g eneratl0n - 



3rd generation ... a 4- b " tf " / ) ... 



c + ^ " «-«A f 4th g eneratlon - 



The significance of the word "or" in the above table is 

 that different group-names are given to the children accord- 

 ing as to whether "a" &c, &c, is male or female. The above 

 scheme of marital arrangements shows that the progeny of 

 the four first groups (a, b, c, &), have to cross-marry in the 

 second generation according to the four second groups 

 (e, f, g, h). Their progeny again cross-marry in the third 

 generation, and are called by the same group names as the 

 original four first groups. This complete and systematic in- 

 tercrossing for three generations causes the principle of here- 

 dity to swamp any tendency to divergent or polytypic evolu- 

 tion. Whatever tendency there may have existed to varia- 

 bility would under these conditions have been all in one 

 direction, and have been the mean of the whole, producing a 

 monotypic evolution, b>ecause, as Romanes points out, na*- 

 tural selection alone can never produce polytypic, but only 

 monotypic evolution. The marriage laws of the Australian 

 aborigines are seen, therefore, to favor the maintenance of a 

 uniformity of type. 



Isolation. — As has been mentioned, isolation is a generic 

 term having species, sub-species, forms, and cases. As a 

 genus the isolation of the Australian aboriginal has been a 

 marked one, and, comparatively speaking, a complete one, 

 from the rest of humanity. As a species of isolation it may 

 be put under the heading of homogamous or discriminate 

 isolation ; that is, the breeding of like with like. There is 

 no evidence of this race having been separated from any 

 parent stock, nor do there exist any traditions pointing to 

 any such past, b>ut everything seems to confirm the idea that 

 they are part and parcel of their environment, or, in other 

 words, autochthonous. The isolation, therefore, has been 

 essentially discriminate. It has been pointed out that that 

 sub-species of homogamy called natural selection, which is the 

 exclusive breeding between those best adapted to their en- 

 vironment, is ineffective to produce divergence of type un- 

 assisted, except in one direction, but that its effects may be 

 cumulative; or, as Pearson writes, it may be occupied with 

 checking, guiding, and otherwise controlling a progressive 



