500 THE ANTIQUITY OF MAN 
of our search in the aboriginal Australian. He is an 
ancient and generalised type of humanity ; he is not the 
direct ancestor of either African or European, but he 
has apparently retained the characters of their common 
ancestor to a greater degree than any other living race. 
If, then, we accept the Australian native as the nearest 
approach to the common ancestor of modern mankind, 
can we form any conception of the length of time which 
would be required to produce the African on the one 
hand, and the European on the other, from the Australian 
type .? From what we have seen in Egypt, in Europe, 
and in North America it is certain that a human type 
can persist for many thousands of years. A human 
type changes very slowly. Therefore, we must make 
a liberal allowance of time for the mere differentiation of 
the modern type of man into distinct racial forms. Even 
if we admit that the ancestral type from which all modern 
races of men have descended was as highly evolved as 
the Australian native, I do not think that any period 
less than the whole length of the Pleistocene period, 
even if we estimate its duration at half a million of 
years, is more than sufficient to cover the time required 
for the differentiation and distribution of the modern 
races of mankind. 
The proof that man of a modern build of body was 
in existence by the close of the Pliocene period is 
presumptive, not positive. So far, we have no certain 
trace of the type beyond the middle of the Pleistocene. 
We presume a greater antiquity in order to obtain a 
working hypothesis which will explain the facts now at 
our disposal. The human genealogical tree, given in 
fig. 187, represents, in a concrete form, the anthropologist's 
working hypothesis. An inspection of that figure will 
show the reader how little we know of the ancestry of 
modern races. Of the fossil predecessors of the Australian 
native race we know nothing. With the possible exception 
of the discovery made by Dr Hans Reck, we have not 
found as yet a single trace of the Pleistocene ancestry 
of the negro. The discovery reported by Dr Hans 
I 
