CnAh II. Manner of Development. 47 



gularly to destroy their own offspring, or to be quite devoid of 

 jealousy. There would have been no prudential restraint from 

 marriage, and the sexes would have freely united at an early age. 

 Hence the progenitors of man would have tended to increase 

 rapidly ; but checks of some kind, either periodical or constant, 

 must have kept down their numbers, even more severely than 

 with existing savages. What the precise nature of these checks 

 were, we cannot say, any more than with most other animals. 

 We know that horses and cattle, which are not extremely prolific 

 animals, when first turned loose in South America, increased at 

 an enormous rate. The elephant, the slowest breeder of all 

 known animals, would in a few thousand years stock the whole 

 world. The increase of every species of monkey must be 

 checked by some means; but not, as Brehm remarks, by the 

 attacks of beasts of prey. No one will assume that the actual 

 power of reproduction in the wild horses and cattle of America, 

 was at first in any sensible degree increased ; or that, as each 

 district became fully stocked, this same power was diminished. 

 No doubt in this case, and in all others, many checks concur, 

 and different checks under different circumstances ; periodical 

 dearths, depending on unfavourable seasons, being probably the 

 most important of all. So it will have been with the early pro- 

 genitors of man. 



Natural Selection. — We have now seen that man is variable in 

 body and mind ; and that the variations are induced, either 

 directly or indirectly, by the same general causes, and obey the 

 same general laws, as with the lower animals. Man has spread 

 widely over the face of the earth, and must have been exposed, 

 during his incessant migrations, 63 to the most diversified con- 

 ditions. The inhabitants of Tierra del Fuego, the Cape of Good 

 Hope, and Tasmania in the one hemisphere, and of the Arctic 

 regions in the other, must have passed through many climates, 



" fall of man. He shews that the " by the many foul customs, es- 



" instincts of the higher animals " pecially as to marriage, of savage 



" are far nobler than the habits of " tribes. What does the Jewish 



" savage races of men, and he finds ' ; tradition of the moral degenera- 



" himself, therefore, compelled to " tion of man through his snatching 



" re-introduce, — in a form of the " at a knowledge forbidden him 



" substantial orthodoxy of which he " by his highest instinct assert 



" appears to be quite unconscious, — " beyond this ?" 



" and to introduce as a scientific 63 See some good remarks to this 



u hypothesis the doctrine that man's effect by \V. Stanley Jevons, "A 



" gain of knowledge was the cause of " Deduction from Darwin's Theory," 



* a temporary but long-enduring ' Nature,' 1869, p. 231. 

 " moral deterioration, as indicated 



