58 CONTROLLED NATURAL SELECTION 



It is possible to arrive at the same con- 

 clusion in other ways. There is evidence 

 that the destruction of wild animals is in 

 many respects similar to that observed in 

 man : and that an animal life-table is very 

 like a human one. Many are born to die 

 almost at once : some die before reaching 

 maturity ; others become adults ; and a few 

 only reach old age. It has therefore been said 

 that Natural Selection acts chiefly upon the 

 young, and therefore must be most effective 

 before the assumption of adult characters : 

 and thus cannot be a powerful force in Evo- 

 lution. But this is a false argument, apart 

 from consideration of juvenile characters. 

 Consider one thousand individuals, and sup- 

 pose that ten of these become reproductively 

 mature ; then it is obvious that the death of 

 one of these ten will be equivalent to the 

 destruction of one hundred newly born in- 

 dividuals ; which means that the power of 

 Natural Selection, re Evolution, when adults 

 are operated upon, is a hundred times as great 

 as when newly born individuals are dealt with, 

 and still greater when the adults are about 

 to reproduce. It follows, therefore, that the 

 factors which decide life or death of adults 

 are very important ones of Natural Selection. 



