Xo. 485] THE DETERMINATION OF SEX 



315 



IV. The Biological Significance of the Sexual Ratio. 



Rauber, apparently taking the view that an excess of females is 

 the normal condition, explains the present preponderance of male 

 births in man by supposing that those tribes or families which, 

 in primitive times, had the greatest proportion of males would 

 possess a certain advantage in warfare and thus be enabled to 

 overpower those in which there was a larger proportion of females. 

 The male preponderance, once estabhshed, would be perpetuated 

 by heredity. This ingenious explanation, does not, however, 

 account for the excess of females among the domestic animals. 

 What the sexual ratio was in primitive man we have no means of 

 knowing. Neither do we know what the sexual ratio was in horses 

 and sheep before they were domesticated. One would expect 

 that the sexual ratio in wild animals would de})end somewhat 

 upon the mating and breeding habits of a species. In those species 

 of birds, in which one male mates with one female for a season or 

 for Hfe, we might expect that the sexual ratio would be nearly 

 unity, the excess of one sex or the other depending on which one 

 was exposed to the greater dangers and had the less chance of 

 growing to maturity. In herds of wild horses, cattle and ])i.s()ii, 

 there are many females to one male. All but the .stn)ii<:(\sr nialf> 

 are killed off by the others and the number of adult males is thu> 

 kept down to 'the needs of the herd. Those iii.livi.hials which 



than males, and it is iM)>sil)le, in fact nioiv than pi-obablc. that man 

 has unconsciously, by selection in breeding, increased the pro- 



No one sexual ratio may be taken as the standard. — If sex is 



herclitary, we ini-lit reasonal)ly expect that the relative mnnbers 

 of male and female births in any species would be those which, 



at the period Of sexual' niatm-ity of its individuals the irrlatest 

 advantage in the >trn,uol,. for exist^uv so far as the pnMlu.-tion of 



enj.uMhe maxiinuni reproductive power, and this cnn'diiiun would 

 be fulfilled when there were no superfluous, sexually mattu-e males 

 or females. 



