5IO THE ANTIQUITY OF MAN 
which led on to the great anthropoid apes, then it is 
apparent from fig. 189 that the antiquity of man covers 
an immense period of time. On the scale of time re- 
presented in fig. 189, which is based on estimates published 
by Professor Sollas/ a period of about two million years 
has elapsed since the separation of the human stem, 
provided, of course, that the hypothesis represented by 
fig. 189 is approximately right. That tree probably 
errs in underestimating rather than overestimating the 
antiquity of the human stem. 
When we speak of the antiquity of man, however, 
most of us have in mind not the date at which the 
human lineage separated from that of the great anthro- 
poids, but the period at which the brain of man had reached 
a human level or standard. We may take the lower limits 
of the brain capacity in modern living races, say 1000 c.c, 
as a working standard. If it is arbitrary it is also con- 
venient. If, then, we propose to estimate the antiquity 
of man from the appearance of human types with average 
brain capacities of 1000 c.c. or more, we must still regard 
man as an ancient form, with a past immeasurably longer 
than is usually believed. From what we know, and 
from what we must infer, of the ancestry of Eoanthropus, 
of Neanderthal man, and of modern man, we have 
reasonable grounds for presuming that man had reached 
the human standard in size of brain by the commencement 
of the Pliocene period. From fig. 189 it will be seen that 
the Pleistocene and Pliocene periods are estimated to cover 
a period of about one million years. That period, on the 
grounds defined above, represents the antiquity of man. 
Perhaps the most important and the most convincing 
source of evidence relating to man's antiquity is one 
which has been kept unduly in the background throughout 
this book. We cannot have more certain evidence of man's 
existence than the implements which he has shaped and 
used. We have seen how long it took to convince the 
modern world that the palaeoliths in the gravel deposits 
of Western Europe were shaped by man's hand. Now 
^ See reference on p. 307. 
