422 CLIMATE AND BRAIN. 



species ; since that time however, the human hody has 

 been but slightly changed, the distinctions which exist 

 between the races of men being unimportant and 

 external. Such as they are, they have been produced 

 by differences of climate and food acting indirectly 

 upon the races throughout geological periods ; and it 

 is also possible that these distinctions of hair and skin 

 were chiefly acquired at a time when man's intelli- 

 gence being imperfectly developed, his physical or- 

 ganisation was more easily moulded by external 

 conditions than was afterwards the case. For while 

 with the lower animals the conditions by which they 

 are surrounded can produce alterations throughout 

 their whole structure, or in any part ; with men, they 

 can produce an alteration only in the brain. For in- 

 stance, a quadruped inhabits a region which, owing to 

 geological changes, is gradually assuming an Arctic 

 character. In the course of some hundreds or thou- 

 sands of centuries the species puts on a coat of warm 

 fur, which is either white in colour, or which turns 

 white at the snowy period of the year. But when man 

 is exposed to similar conditions he builds a warm house 

 and kills certain animals, that he may wear their 

 skins. By these means he evades the changed con- 

 ditions so far as his general structure is concerned. 

 But his brain has been indirectly altered by the 

 climate. Courage, industry, and ingenuity, have been 

 called forth by the struggle for existence ; the brain 

 is thereby enlarged, and the face assumes a more in- 

 telligent expression. Of such episodes the ancient 

 history of man was composed. He was ever contend- 

 ing with the forces of nature, with the wild beasts of 

 the forest, and with the members of his own species 

 outside his clan. In that long and varied struggle 



