SEXUAL SELECTION. 211 



to investigate, as far as I could, the proportions betwean the two 

 sexes of as many animals as possible; but the materials are 

 scanty. I will here give only a brief abstract of the results, re- 

 taining the details for a supplementary discussion, so as not to 

 interfere with the course of my argument. Domesticated ani- 

 mals alone afford the means of ascertaining the proportional 

 numbers at birth; but no records have been specially kept for 

 this purpose. By indirect means, however, I have collected a con- 

 siderable body of statistics, from which it appears that with 

 most of our domestic animals the sexes are nearly equal at birth. 

 Thus 25,560 births of race-horses have been recorded during 

 twenty-one years, and the male births were to the female births 

 as 99.7 to 100. In greyhounds the inequality is greater than with 

 any other animal, for out of 6878 births during twelve years, the 

 male births were to the female as 110.1 to 100. It is, however, in 

 some degree doubtful whether it is safe to infer that the propor- 

 tion would be the same under natural conditions as under do- 

 mestication; for slight and unknown differences in the conditions 

 affect the proportion of the sexes. Thus with mankind, the male 

 births in England are as 104.5, in Russia as 108.9, and with the 

 Jews of Livonia as 120, to 100 female births. But I sha;i recur 

 to this curious point of the excess of male births in the supple- 

 ment to this chapter. At the Cape of Good Hope, however, male 

 children of European extraction have been born during several 

 years in the proportion of between 90 and 99 to 100 female chil- 

 dren. 



For our present purpose we are concerned with the proportion 

 of the sexes, not only at birth, but also at maturity, and this adds 

 another element of doubt; for it is a well ascertained fact that 

 with man the number of males dying before or during birth, and 

 during the first few years of infancy, is considerably larger than 

 that of females. So it almost certainly is with male lambs, and 

 probably with some other animals. The males of some species 

 kill one another by fighting; or they drive one another about 

 until they become greatly emaciated. They must also be often 

 exposed to various dangers, whilst wandering about in eager 

 search for the females. In many kinds of fish the males are 

 much smaller than the females, and they are believed often to be 

 devoured by the latter, or by other fishes. The females of some 

 birds appear to die earlier than the males; they are also liable to 

 be destroyed on their nests, or whilst in charge of their young. 

 With insects the female larvae are often larger than those of the 

 males, and would consequently be more likely to be ae- 

 voured. In some cases the mature females are less active and 

 less rapid in their movements than the males, and could not es- 

 cape so well from danger. Hence, with animals in a state of na- 

 ture, we must rely on mere estimation, in order to judge of the 



