136 THE DESCENT OF MAN. Part I. 



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 and changed their habits many- 

 times, before they reached their present homes. 57 The 

 early progenitors of man must also have tended, like all 

 other animals, to have increased beyond their means of 

 subsistence ; they must therefore occasionally have been 

 exposed to a struggle for existence, and consequently to 

 the rigid law of natural selection. Beneficial variations 

 of all kinds will thus, either occasionally or habitually, 

 have been preserved, and injurious ones eliminated. I 

 do not refer to strongly-marked deviations of structure, 

 which occur only at long intervals of time, but to mere 

 individual differences. We know, for instance, that the 

 muscles of our hands and feet, which determine our 

 powers of movement, are liable, like those of the lower- 

 animals, 58 to incessant variability. If then the ape-like 

 progenitors of man which inhabited any district, espe- 

 cially one undergoing some change in its conditions, were 

 divided into two equal bodies, the one half which in- 

 cluded all the individuals best adapted by their powers 

 of movement for gaining subsistence or for defending 

 themselves, would on an average survive in greater 

 number and procreate more offspring than the other 

 and less well endowed half. 



Man in the rudest state in which he now exists is 

 the most dominant animal that has ever appeared 

 on the earth. He has spread more widely than any 



37 Latham, ' Man and his Migrations,' 1851, p. 135. 



58 Messrs. Murie and Mivart in their " Anatomy of the Lemuroidea" 

 (' Transact. Zoolog. Soc.' vol. vii. 1869, p. 96-98) say, " some muscles 

 " are so irregular in their distribution that they cannot be well classed 

 " in any of the above groups." These muscles differ even on the oppo- 

 site sides of the same individual. 



