NOMADISM, WITH SPECIAL REFERENCE TO HEREDITY. 9 



III. THE WANDERING INSTINCT. 



A tendency to wander in some degree is a normal characteristic of 

 man, as indeed of most animals, in sharp contrast to most plants ; and 

 the well-developed locomotor appendages of the higher animals are 

 correlated with this tendency to move about, be it to seek food, mates, 

 or shelter. In many species the instinct drives an animal to travel far 

 over the earth's surface; thus some migrating birds traverse, twice a 

 year, 60 degrees of the earth's surface or 3,600 miles. On the other 

 hand, certain birds are permanent residents of any place, i. e., they do 

 not travel more than a few miles ; for example, many ground birds and 

 other birds of tropical or subtropical oceanic islands. Now, whether 

 a species tends to travel far or tends to stay near its home depends upon 

 its constitutional factors — its instincts. The differences between men 

 in respect to these points are as truly specific as the differences between 

 swallows and grouse, and are as truly due to differences in inherited 

 instincts. 



The fact that in an individual man the strength of the wandering 

 instinct varies may be regarded as evidence that it is not a constitu- 

 tional trait. Of these variations there can be no doubt. In typical 

 manic-depressives the same individual may at one time fail to respond 

 to a stimulus which at another time causes extraordinary outbursts of 

 activity. As our family histories show, the nomadic may be con- 

 tented at home for weeks or even months and then suddenly follow 

 the impulse to go away. Many persons who are nomadic in their 

 youth settle down in later years. But these facts, instead of militating 

 against the view that nomadism in man is of the same order as that 

 of birds, support the view, for the migrating birds feel the impulse to 

 migrate periodically — twice a year — and the same is true of certain 

 migrating mammals ; and that the nomadic instinct should fail later in 

 life is just what the sexual and many other instincts do. 



I,est the argument for a wandering instinct based on a comparison of 

 man with birds may seem far-fetched, four other sets of facts may here be 

 adduced : (i) that the wandering instinct is in the anthropoid apes, which 

 show the same basal instincts that man does; (2) that many if not 

 most primitive peoples are migratory; (3) that the tendency to run 

 away is extraordinarily frequent among young children; and (4) that 

 the adolescent period, when all instincts (and especially those in any 

 way connected with sex) are brought to the surface, is perhaps the 

 commonest period for running away. This evidence we shall consider 

 in detail. 



1. THE WANDERING INSTINCT IN ANTHROPOID APES. 



That the chimpanzee and the gorilla are nomadic in their native 

 forest and "seldom or never pass two nights in the same spot" is 

 asserted by Gamer (1890, p. 97), who has probably studied them at 

 home more thoroughly than any other man. Of the gorilla he says 



