LIFE THE TRAVELER 
would have to be in every one thousand years to 
bring it about in geologic or biologic time? 
Where does such an estimate leave natural selec- 
tion? Of what survival advantage to the eohippus 
could the gain of an inch in height in forty thou- 
sand years, or of one pound of weight in four hun- 
dred years, amount to? Such an application of 
mathematics to the problems of evolution leaves 
us with the conviction that there is something else 
at work besides natural selection. Could natural 
selection work on a capital of a gain of the one one- 
hundredth of an inch in height in four hundred 
years? — assuming, of course, that the gain was 
uniform. Must there not have been an inherent 
tendency to increase in size and to all the various 
modifications —a primal push, as Bergson urges? 
With man it has, no doubt, been the same. His 
evolution has been so infinitely slow, that the me- 
chanical conception of it is utterly inadequate. It 
is very certain that his line of descent in Miocene 
times was through a small animal form probably 
no larger than a new-born baby. 
Or take the case of the elephant. These forms 
changed and enlarged under the discipline of their 
environment, the augmenting force or impulse 
within always meeting and filling the changing 
needs from without. The size of the channel of the 
stream kept pace with the increasing size of the 
stream. The stream branches or divides when some 
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