2S6 THE DESCENT OP MAN. 



baboons, it is conceivable that a male-producing tendency miglit 

 be gained by natural selection; for the individuals of the better 

 defended herds would leave more numerous descendants. In 

 the case of mankind the advantage arising from having a pre- 

 ponderance of men in the tribe is supposed to be one chief cause 

 of the practice of female infanticide. 



In no case, as far as we can see, would an inherited tendency 

 to produce both sexes in equal numbers or to produce one sex 

 in excess, be a direct advantage or disadvantage to certain in- 

 dividuals more than to others; for instance, an individual with 

 a tendency to produce more males than females would not succeed 

 better in the battle for life than an individual with an opposite 

 tendency; and therefore a tendency of this kind could not be 

 gained through natural selection. Nevertheless, there are certain 

 animals (for instance, fishes and cirripedes) in which two or more 

 males appear to be necessary for the fertilization of the female; 

 and the males accordingly largely preponderate, but it is by no 

 means obvious that this male-producing tendency could have been 

 acquired. I formerly thought that when a tendency to produce 

 the two sexes in equal numbers was advantageous to the species, 

 it would follow from natural selection, but I now see that the 

 whole problem is so intricate that it is safer to leave its solution 

 for the future. 



