384 MARTIN P..NILSSON 

condition for the developing of a race is that a group of men, who 
may be counted in hundreds or in millions, shall live for a con- 
siderable time in at least relative isolation, so that foreign disturbing 
elements are kept out. If it be supposed that this group originally 
contained a motley mixture of internal and external dispositions, the 
natural conditions under the sway of which the group lives will be 
favourable for some of these dispositions and unfavourable for others. 
The natural conditions have the same effect as the conscious inter- 
ference of a breeder trying to produce a certain race of some species 
of animals, although more slowly and not to the same extent. The 
effect will be stronger in proportion to the smallness of the group 
and the intensity of inbreeding. The outcome of this selection de- 
pends much more on the dispositions which originally existed and 
which in the development of the race attain to ascendency than on 
the external milieu. Why some races are excellently adapted to the 
natural conditions of life of their country and are yet unable to achieve 
a higher political and intellectual development, and why on the other 
hand other races are able to create a culture and a political organiza- 
tion is a riddle which is concealed in the darkest riddle of all, the 
human mind, the variability of intelligence and volition, for these too 
are properties which vary with the race. It is only that we cannot 
grasp them definitely. 
Primitive conditions are favourable to this breeding of races. The 
population is thin and split up into small groups. Intercourse is 
rare. The tribes are hostile or at least foreign to each other and 
occupy each a definite district. A fact of profound importance for 
the development of society and races is the claim to possess the di- 
strict in which the tribe lives; this seems to be founded in the nature 
of man, as well of some species of animals. Foreigners who pene- 
trate into the district of the tribe will be expelled or killed. The tribe 
maintains its purity from foreign elements until the advance of cul- 
ture introduces slavery, which is first applied to the women. In pri- 
mitive conditions this occasion of the mixing of the races is of no 
great extent or importance. Neighbouring tribes are often kindred. 
Under primitive conditions we have consequently to expect a mul- 
tiplicity of characteristically different races, although the differing ca- 
pacity of different races to maintain themselves in the struggle for life 
and the combats against other races causes a certain race to spread 
itself over a wider territory, while the migrations which originate in 
over-population and an innate desire to wander introduce a foreign 
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