SELECTION ON MAN. all 
slow, for the changes in the universe are very slow ; 
but just as these slow changes become important, when 
we look at results after long periods of action, as we 
do when we perceive the alterations of the earth’s sur- 
face during geological epochs; so the parallel changes 
in animal form become more and more striking, in 
proportion as the time they have been going on is 
great; as we see when we compare our living animals 
with those which we disentomb from each. successively 
older geological formation. 
This is, briefly, the theory of “natural selection,” 
which explains the changes in the organic world as 
being parallel with, and in part dependent on, those in 
the inorganic. What we now have to inquire is,— 
Can this theory be applied in any way to the question 
of the origin of the races of man? or is there anything 
in human nature that takes him out of the category 
of those organic existences, over whose successive 
mutations it has had such powerful sway ? 
Different effects of Natural Selection. on Animals and 
on Man. 
In order to answer these questions, we must consider 
why it is that “ natural selection” acts so powerfully - 
upon animals; and we shall, I believe, find, that its 
effect depends mainly upon their self-dependence and 
individual isolation. A slight injury, a temporary 
illness, will often end in death, because it leaves the 
individual powerless against its enemies. If an herbi- 
vorous animal is a little sick and has not fed well for a 
