140 The Journal 
words, there arose warm-blooded ani- 
mals whose temperature was more or 
less independent of the surrounding air 
instead of varying with it as is the case 
in cold-blooded animals. | Among 
mammals this led to the production of 
the young within the body of the 
mother, instead of from eggs in which 
the mother took little or no interest 
after they were laid. Among birds it 
forced the mother to care for the eggs 
if they were to be hatched. Thus the 
relation of mother and child became 
firmly established. The latter develop- 
ment of this relation has been the chief 
source of all that is best in mankind.” 
THE AGE .OF REPTILES 
All this, of course, was a slow de- 
velopment. Gigantic reptiles lorded it 
on the earth in those days, and the 
mammals were little beasts skulking 
in out-of-the-way corners, perhaps in 
the hills rather than on the lowland 
plains. 
“Once more we must skip millions 
of years. The mammals have grown 
in size and variety until they range 
from the mouse to the mammoth. They 
have ousted the reptiles from the best 
parts of the earth. They have taken to 
the air with the wings of the bat, they 
have gone back to sea with the whale, 
they have learned to run like the ante- 
lope, to burrow like the mole, and to 
climb trees like the squirrel. Their 
limbs have become hoofs, claws, wings, 
flippers, and hands. The Age of Mam- 
mals has come to its epiphany. Then 
as in Permian times, there once more 
comes a widespread period of climatic 
stress, the last Glacial Period. A new 
element enters into its evolution, for 
at last man appears and intelligence be- 
comes dominant. 
“When the mammals had reached a 
condition of complete dominance they 
were suddenly wiped out wholesale. In 
North America the whole family of 
horses was destroyed; the elephant 
tribe, including the mammoth and 
mastodon, disappeared; the camel, 
which had formerly been abundant, 
passed away, leaving no trace save his 
of Heredity 
bones. Still other great families such 
as the giant beaver, the sloth, the tapirs, 
and the so-called glyptodonts were like- 
wise exterminated. In Europe there 
was a similar appalling destruction of 
life. 
“Directly or indirectly all this de- 
struction arose from the severe climatic 
oscillations of the Glacial Period, for 
this one period included four great 
‘epochs.’ It was apparently the 
Glacial Period which chiefly stimulated 
man’s mental development and caused 
his intelligence to dominate the earth. 
Previous to the Glacial Period the 
brain of man’s animal ancestors had 
been evolving very slowly for hundreds 
of millions of years. During the half 
million years more or less of the Glacial 
Period previous to the time we have 
now reached, that is, previous to the 
last Interglacial Epoch, it had been in- 
creasing at a rate vastly faster than 
formerly. Yet at the time of the Pilt- 
down Man [100,000 to 150,000 B. C.?] 
the human animal, as we may perhaps 
still call him, had made almost no ad- 
vance in the use of material resources. 
His weapons were probably nothing but 
stones, bones, and sticks that he broke 
with his hands. His most elaborate 
manufactured instruments were flints 
of the rudest sort. These were merely 
thick chips roughly flaked a little to in- 
crease their cutting power. So far as 
we yet know, man was still ignorant of 
the use of fire. 
THE NEANDERTHAL RACE 
“In those days the climate of Central 
Europe was apparently somewhat 
milder than at present. This mild 
climate continued for a long time, ap- 
proximately 50,000 years according to 
Osborn’s chronology, which we are now 
following. During this time the region 
from northern Spain and Italy to south- 
ern England and western Austria, 
whence our knowledge of early man is 
chiefly derived, {was peopled by the 
Neanderthal race. These people ap- 
pear to have been a little more ad- 
vanced than the Piltdown type, but 
their brains were distinctly smaller than 
