EVENING DISCOURSES. 785 
dotage, and we do not begin to find their normally fish-shaped ancestors until we 
go so far back as the Chalk. 
It is also curious to note how close is the parallelism in some cases between 
the history of a race in geological time and the individual life-history of one 
of its latest members. The deer, for instance, had no horns or antlers before 
the Lower Miocene period; but since that time the successive species have 
gradually acquired antlers of increasing size and complexity, and those of 
some of the Pleistocene and later deer were so immense that they probably 
helped in the extinction of these animals. Exactly similar stages are passed 
through in the individual life-history of the common stag at the present day : 
when born it has no antlers, in the second year they are a pair of simple 
prongs, while in each succeeding year they become increasingly large and 
complex. 
In fact, when any particular part of an animal begins to grow to a larger 
size, this growth tends to continue long after it appears to attain its special 
usefulness. Sometimes this leads to fundamental changes which turn the 
overgrowth from a burden to a decided advantage. For example, as soon as 
warm-blooded quadrupeds (mammals) appeared, the brain in these animals 
tended to grow large and complex. So long as there were no higher back- 
boned animals than reptiles the brain always remained insignificant in size. 
Among mammals this enlargement was obviously of some importance, because 
whenever members of this group grew large or showed special adaptations to 
a peculiar mode of life without a corresponding development of the brain they 
soon died out. Thus, our horses, cattle, lions, dogs, and so forth have only 
survived because the changes in the efficiency of their brain have kept pace 
with the special changes in the rest of their body. At the same time, during 
the whole of the Tertiary period, while these correlated changes in brain and 
body were taking place in the majority of mammals, one group remained as 
forest-dwellers. In them the skeleton, and presumably most of the soft parts, 
underwent practically no change, while the brain alone developed in size and 
efficiency. The little lemur-like animals of Hocene times thus passed gradually 
into the comparatively large apes of the Pliocene. Compared with the rest 
of the body, the brain tended to be overgrown, and it seems reasonable to 
suppose that this overgrowth eventually led to the complete domination of 
the brain which is the special characteristic of man. As soon as an animal 
could feed and defend itself by craft, its teeth and other primitive weapons 
would degenerate. 
We have long been looking for the links that are missing in this hypothe- 
tical chain connecting man with the early forest animals, because, apart from 
adaptation to an upright gait, his skeleton is practically identical with theirs. 
We have looked for creatures with an overgrown brain and ape-like face, but 
hitherto without real success. The scientific world has therefore welcomed 
with great interest Mr. Charles Dawson’s recent discovery of the skull and 
mandible of Hoanthropus dawsoni, the most primitive human being ever 
seen. The gravel in which it was found at Piltdown, in Sussex, dates back 
to the geological period when we might expect the earliest men to be just 
appearing; and the circumstances of its discovery leave no doubt that it 
was contemporaneous with the very rude flint implements which were lying 
in the same deposit near it. 
When I first planned this lecture, I intended to speak at greater length 
and with fuller illustrations of the interesting general principles to which I have 
alluded, and then apply them to discuss the meaning of this latest missing 
link among extinct animals. The very conclusion as to its being a missing 
link, however, has been so much disputed lately in the newspapers that I 
am compelled to spend some time in a digression to assure you first of the 
facts. In my original description and interpretation of Mr. Dawson’s dis- 
covery I stated that the skull of Hoanthropus, though typically human, was 
as low in brain-capacity as that of the lowest existing savages, while Prof. 
Elliot Smith asserted that the brain itself, as shown by the cast of the cavity, 
was of a more primitive kind than any human brain he had previously seen. 
I also concluded that, as the lower jaw exhibited so many ape-like characters, 
it must have been furnished in front with ape-like teeth, including enlarged 
1913. 35 
