1908-9. ] HuMAn EvoLuTION AND HUMAN DISEASE. 545 
ually permeate and destroy the race, but here again it is a factor in natural 
selection and where leprosy existed in continental areas such as Europe, 
the naturally immune survived and the disappearance from the Con- 
tinent of Europe of this disease must have been as much due to surviving 
natural immunity as to the somewhat incomplete sanitary measures of 
the centuries which preceded the nineteenth. 
The recent spread of Sleeping Sickness from West Africa into Uganda, 
with the result that tribes living about Lake Victoria, have been practically 
wiped out, illustrates the ruthless way in which disease selection sometimes 
works. In this instance there is so far as we know at present no recovery 
and no immunity is therefore established, but the selective influence leads 
to the destruction of tribes living in the area in which the Glossina fly 
is found, whilst having no effect upon tribes dwelling in healthier sur- 
roundings. 
A most interesting suggestion has been made by Dr. Archdale Reid 
in his studies upon heredity in regard to the effect of alcohol upon the 
human race. In alcohol we have an example of a poison the discovery 
of which is comparatively recent in human evolution. One of its most 
striking effects is upon aboriginal races who have been brought in contact 
with it by white men. ‘These races succumb rapidly to it and the race 
deteriorates and dies out. Yet we know that there are nations where 
alcohol, in the form of light wines, is used continuously and freely without 
any evidence of racial deterioration. Reid’s position is that the longer 
a race has been in contact with alcohol, the more thoroughly is drunken- 
ness eliminated, since those who develop alcoholism die out and leave fewer 
descendants, while those who are temperate persist. The ultimate result 
is the selection of a race who have come to use the less intoxicating alcoholic 
drinks in moderation. ‘The Mediterranean Europeans are, according to 
him, examples of the ultimate results of selection; the northern races, of 
the intermediate stage and aboriginal races of the first stage. 
A natural objection to raise to this view is that Mohammedans have 
refrained from the use of alcohol on religious grounds, yet there is no 
evidence that they show greater susceptibility to its effects and especially 
to the development of alcoholics than less temperate people. There are 
other objections, but it must be admitted on a priori grounds that an 
unlimited exposure of a race to the use of alcohol would in the course of 
generations eliminate the intemperate. It would, however, take a very 
long time, and again, we find among the nations the characteristic attitude 
of the human race towards all natural selective influences and by education 
and legislation an attempt is made to hurry the evolution. Whether we 
will be successful remains to be seen. 
