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 
57 Latham , 1 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. 
