A CHAPTER OF CONCLUSIONS 499 
been evolved. If, therefore, we try to form a picture 
of the world of ancient and primitive humanity, we must 
base it on the conditions now existing among anthropoids, 
not on those which hold for the modern world of 
mankind. We should expect, then, when we go far 
enough back, to find humanity broken up into distinct 
structural groups or genera, each confined to a limited 
part of the earth. Inside each group we expect to find, 
as amongst the great anthropoids, a tendency to produce 
varieties or species. We have seen that many facts 
relating to ancient man which were formerly obscure 
or conflicting become easy of comprehension when this 
interpretation is applied. 
Another line of evidence ought to have raised a 
suspicion that we were underestimating the antiquity 
of man in our earlier speculations. The anthropologist, 
when he seeks for an explanation of the evolution and 
distribution of modern races of mankind, finds it necessary 
to make a large demand on the bank of time. We all 
agree that modern human races, however different they 
may appear, are so alike in the essentials of structure 
that we must regard them as well-marked varieties of 
a common species. Let us look at the problem of their 
evolutio^i in a concrete form, taking as opposite and 
contrasted types of modern humanity the fair-haired, 
white-skinned, round-headed European and the woolly- 
haired, black-skinned, long-headed negro of West Africa. 
We shall set those two contrasted types side by side and 
study them from a purely zoological point of view. 
We must admit that both are highly specialised types ; 
neither represents the ancestral form. Now, in seeking 
for the ancestral form of our breeds of dogs, of horses, 
or of cattle, we select one of a generalised and ancient 
type, such as we conceive might have become modified 
into various modern breeds. We must apply the same 
method to the elucidation of human races. If we search 
the present world for the type of man who is most likely 
to serve as a common ancestor for both African and 
European we find the nearest approach to the object 
