A CHAPTER OF CONCLUSIONS 507 
anthropoid apes, we may obtain collateral evidence bearing 
on the date at which the differentiation of the human 
body became possible. To save description, I have 
represented the present state of our knowledge of anthro- 
poid evolution in the form of a genealogical tree (fig. 
188). The stems of the three great anthropoids — the 
gorilla, chimpanzee, and orang — are seen to join together 
in the older part of the Pliocene period. We have not 
many facts to guide us. We know of a late Pliocene 
anthropoid — Palaeopithecus — which shows relationships 
to both chimpanzee and orang, but was probably not 
a direct ancestor of either. AVe know that the great 
anthropoids were already evolved in the Miocene period. 
Dryopithecus was alive in that period, and was about 
the size of the chimpanzee, but more primitive in features 
of tooth and jaw. We know, too, that the small anthro- 
poids — the gibbons — were already in existence in the 
Miocene period. So far as our knowledge goes, the 
Miocene anthropoid apes offer us no form which can 
serve as a probable human ancestor. The small and 
large anthropoids were already differentiated, and we 
may presume that the same was the case with the 
human form. Hence in fig. 188 the stems of the 
small anthropoids, of the great anthropoids, and of man 
are represented as already separated in the Miocene 
period. The evidence, so far as it goes, justifies us in 
presuming that the human and anthropoid lines of 
descent separated in pre-Miocene times. ^ 
In fig. 189 the anthropoid and human genealogical 
trees have been combined. The tree represents a working 
hypothesis which may require alteration as new facts 
come to light. It is framed so as to account for the 
evolution and structural characters of the various forms 
of ape and man. The discovery of fossil remains of 
extinct forms gives us some guidance as to the probable 
date at which various types became evolved. In framing 
such a genealogical tree it is necessary — at least it seems 
' For a fuller statement of the case, see Reports of British Association^ 
191 2, p. 753 (" Modern Problems relating to the Antiquity of Man "). 
