20 PHYSICAL BASIS OF CIVILIZATION 



dence; nor is the existence of fine, almost invisible 

 hair all over the body ; nor is the hairiness of the six- 

 months-old human embryo. These facts can only be 

 considered as evidence that by variation the "genus 

 homo" has descended from hairy non -human brutes. 



Nor is it reasonable to suppose that the wearing 

 of artificial covering has caused a hairy ancestry to 

 bring forth a hairless progeny, for this is taking the 

 transmission of acquired traits for granted. 



Hairy coats collect and harbor fleas, lice, and 

 similar insect pests on the bodies of animals, and also 

 disease germs, and here these can multiply prodi- 

 giously. The secretions of the skin furnish ideal 

 culture media for these germs, and the crawling 

 and hopping insects can carry them around. Thus 

 it requires but a slight accidental scratch or cut to 

 enable the germs to invade the bodies of their hosts, 

 and it is possible thus to spread devastating epi- 

 demics in herds or entire races. 



Comparative hairlessness, such as exists in the 

 human race, and which under natural conditions is 

 such an inestimable adjunct to cleanliness, must 

 for the reasons stated have been of survival value, 

 and this makes it probable that this trait was nat^ 

 urally selected in the human race. At least it pro- 

 duces such a strong preliminary case in favor of 

 this conclusion, as to throw upon those who deny 

 it the onus of proving the contrary. 



It is otherwise with the quadrumana when in 

 their natural habitats. Woodticks, jiggers, and the 





