THE FUTURE EVOLUTION OF MAN 265 
man species, in its development, has lost a large por- 
tion of its instincts, and has gained, instead, the 
power of intelligent choice and the ability to learn 
by imitation. When these drop away, man without 
his instincts or his intelligence is more helpless than 
the brute. Students of sociology are making clear 
to us that a large portion of the criminality of the 
world, much of the looseness of life, and a large 
part of the alcoholic excesses are due to this taint of 
feeble-mindedness. Recent investigations have made 
it clear that one feeble-minded family in a commu- 
nity may, in the course of years, poison the life of 
an entire state. The Jukes family in New York, the 
Kallikak family in New Jersey, have shown the 
awful possibilities of descent from a single feeble- 
minded ancestor. Prisons, almshouses, and houses 
of shame owe their population in no small degree to 
this bitter curse. It will not be long before society 
will learn to protect itself against such poisoning of 
the human stock. Nothing is more clear to the in- 
vestigator of this subject than that the one over- 
whelming cause for feeble-mindedness is feeble- 
mindedness in the parentage. 
There is one type of mental weakling, known as 
the Mongolian idiot, which may arise right out of 
the heart of an apparently sound family. But the 
number of these is comparatively small. The num- 
