26 
EVOLUTION MADE PLAIN 
their prey, and so, be most apt to survive in 
the struggle against starvation? And which 
among the animals preyed on would run the 
least risk of detection and so be most likely 
to escape destruction? The answer to both 
questions, of course, would be, “Those whose 
colors most nearly conformed to the snowy 
background.” Imagine this process of culling 
out the darker colors continuing for many gen¬ 
erations and we can understand that the white¬ 
ness of all arctic animals would be the inevit¬ 
able result. We can also see why most wild 
animals of our regions are of colors that best 
harmonize with the brown earth and dead 
leaves. Let us keep in mind the fact that while 
we were observing the modification of one 
character, all the favorable variations, how¬ 
ever slight, in every other character that could 
be of the least advantage to those creatures 
were being added up as fast as they appeared. 
After several generations, if for any cause the 
environment were undergoing a radical change, 
or if a species had migrated from a widely dif¬ 
ferent one, a greatly modified animal would be 
the result. However, there can be no mod¬ 
ification in an animal perfectly adapted to its 
environment—provided the environment does 
not change. 
Every organ, and every other part of the 
body, internal and external, of every creature 
in the natural state is subject to modification 
by the law of natural selection, just as was the 
color of the hair or the feathers of polar ani¬ 
mals. 
Man’s method of improving plants and ani- 
