NATURAL SELECTION IN MAN 201 
the defective members of the race and if it does not eliminate 
them directly, it causes or rather augments the death rate of their 
progeny and hence works toward the extirpation of their breed. 
From the standpoint of eugenics the infant mortality that 
results from inherent incompetence or moral depravity has its 
obvious advantages. If stocks such as the Jukes, Kallikaks and 
Tribe of Ishmael had had an infant mortality even higher than it 
was there would be few who would regret the fact. It would have 
been much better had these degenerates never been born. But 
having been brought into the world perhaps the next best thing 
would have been for them to have died young. 
By way of summary the kinds of infant mortality we have 
distinguished may be expressed as follows: 
1. Non-selective elimination. This is of no racial value and not 
only masks the workings of natural selection, but interferes with the 
stringency of its action. 
2. Selective elimination of non-hereditary characters. We might 
consider this a racially impotent form of natural selection. 
3. Selective elimination of characters of value only during infancy. 
Racial effect not beneficial beyond rendering infancy more hardy. 
4. Selective elimination of infantile weakness or defect which would 
produce diminished vigor in later life. 
5. Selective elimination of infants not in themselves weak or imper- 
fect, but who would develop into socially undesirable persons. They 
are eliminated in greater numbers because of the incompetence of 
their parents. 
The last two forms of selection are strongly working in the 
direction of racial advance. 
The doctrine that the human species may be in any way im- 
proved through the selective elimination of infants has been 
opposed on the ground that whatever agencies cause babies to die 
would also involve more or less permanent injury upon the sur- 
vivors. In commenting on those writers who commend a high 
infant death rate on account of its selective value, Dr. Saleeby 
remarks: ‘But waiving here the observation that ‘natural selec- 
