HUNTING AND FISHING EACES 157 



in close proximity to man ; under these conditions there was far 

 more opportunity for bacteria and other micro-organisms to 

 become parasitic than before. The suggestion, therefore, is that 

 most diseases evolved in that relatively recent period when, owing 

 to the increase in skill, men came to live in close proximity under 

 settled conditions. 



This suggestion is supported by two other lines of evidence. 

 It would appear that Australia and America were upon their 

 discovery free from most of the diseases known irpEurope. With 

 regard to the former Davidson says : ' Australia presents us with 

 a spectacle of a continent, from the pathology of which entire 

 classes of diseases, prevalent in other divisions of the globe, were, 

 until comparatively recent times, completely absent. Thus the 

 whole class of eruptive fevers — small-pox, scarlet fever, and 

 measles — so fatal elsewhere, were unknown. Epidemic cholera, 

 relapsing fever, yellow fever, whooping cough, and diphtheria 

 were equally absent, as also was syphilis. . . . Leprosy was absent 

 from the southern continent.' ^ The facts with regard to America 

 are very similar. It has been asserted that the only lethal disease 

 of importance present in America before the visit of Columbus 

 was malaria, and it is worthy of note that malaria is an insect-born 

 disease. The question whether tuberculosis was known in America 

 before the discovery has been studied by Hrdlicka, who concludes 

 that, though it cannot be affirmed that it did not exist, it is highly 

 improbable that it did.^ Again, the marked hability on the part 

 of primitive races to common European diseases points strongly 

 to the fact that no immunity had been evolved against these 

 diseases because they were formerly unknown. Since contact 

 with Europeans has been estabhshed, these races have been swept 

 by epidemics, such as the epidemic of measles which carried off 

 a large proportion of the population of Fiji in 1875. 



It is not to be concluded that most diseases are recent in the 

 ordinary sense of the word, but only when a broad view is taken 

 of human history. It is known, for instance, that tuberculosis, 

 plague, leprosy, and bilharzia existed in ancient Egypt. Where 

 and when diseases originated we cannot say, but the fact that 

 certain widely-spread diseases can be traced to a previously hmited 

 and localized incidence — cholera, for instance, to the Ganges 

 Valley — suggests that such diseases originated in those places in 



* Davidson, Geographical Pathology, vol. ii, p. 565. ^ Hrdlicka, S. I. B. E., 



Bull. 42. 



