HOMINID: 741 
—(1) that, however different the extremes of any two races may 
be in appearance (and it must be admitted that, as advocated by 
many polygenists, the differences are greater than many which are 
considered specific among other animals), every intermediate grada- 
tion can be found through which the one passes into the other, 
and (2) that all races are fertile inter se—are quite conclusive in 
favour of considering Man as representing a single species in the 
ordinary sense in which the word is now used, and of treating of 
all his various modifications as varieties or races. 
The great problem at the root of all zoology, the discovery of a 
natural classification which shall be an expression of our knowledge 
of the real relationship or consanguinity of different forms, is also 
applicable to the study of the races of Man. When we can satis- 
factorily prove that any two of the known groups of mankind are 
descended from the same common stock, a point is gained. The 
more such points we have acquired the more nearly shall we be 
able to picture to ourselves, not only the present, but also the past 
distribution of the races of Man upon the earth, and the mode and 
order in which they have been derived from one another. But the 
difficulties in the way of applying zoological principles to the classi- 
fication of Man are vastly greater than in the case of most animals. 
When groups of animals become so far differentiated from each 
other as to represent separate species, they remain isolated; they 
may ,break up into further subdivisions—in fact, it is only by 
further subdivision that new species can be formed; but it is of 
the very essence of species, as now universally understood by 
naturalists, that they cannot recombine, and so give rise to new 
forms. With the varieties of Man it is otherwise. They have 
never so far separated as to answer to the physiological definition 
of species. All races, as said above, are fertile with one another, 
though perhaps in different degrees. Hence new varieties have 
_ constantly been formed, not only by the segmentation of portions 
of one of the old stocks, but also by various combinations of those 
already established. 
Without entering into the difficult question of the method of 
Man’s first appearance upon the world, we must assume for it vast 
antiquity,—at all events as measured by any historical standard. 
Of this there is now ample proof. During the long time Man 
existed in a savage state—a time compared to which the dawn of 
our historical period is as yesterday—he was influenced by the 
operation of those natural laws which have produced the variations 
seen in other regions of organic nature. The first Men may very 
probably have been all alike ; but when spread over the face of 
the earth and subjected to all kinds of diverse external conditions, 
—climate, food, competition with members of their own species or 
with wild animals,—racial differences began slowly to be developed 
