142 The Journal 
appeared we do not know. They were 
not the ancestors of most of the modern 
Europeans. They may have been fair- 
haired like the Nordics, but they had 
peculiarly broad faces and _ relatively 
narrow heads unlike any of the present 
great races. 
THE GREAT MODERN RACES APPEAR 
“They were displaced by other races, 
the long-headed dark Mediterraneans, 
the broad-headed, brown-haired Alpine 
people, and the tall, fair-haired, blue- 
eyed, long-headed Nordics. These later 
races, which have carried civilization 
forward by leaps and bounds, appear 
to have risen to their present mental 
power during this same last Glacial 
Epoch. The place of their origin is not 
quite certain, but their common center 
was quite surely in Central Asia not 
far from where the Cro-Magnons de- 
veloped. In that same region dwelt the 
ancestors of the races that evolved the 
early civilizations of China, India, and 
Asia Minor, and at least a part of the 
Mesopotamian civilization. There, in 
an environment not quite so severe as 
that of central Europe, these early peo- 
ple developed the art of smoothing 
stone implements and evolved other 
capacities which enabled them to con- 
quer the artistic Cor-Magnons. There, 
too, or else in the not greatly dissimilar 
climate which then prevailed in North 
Africa, the art of copper smelting was 
invented. A little later, in essentially the 
same Asiatic regions, the far greater 
art of making iron tools was developed, 
and man took still another of the great 
steps which mark his advance toward 
civilization. 
“In view of these facts and many 
others it is hard to avoid the conclusion 
that the last Glacial Epoch and the 
succeeding period of less pronounced 
climatic changes were peculiarly stimu- 
lating to mental development. The cold- 
est places were not favorable, but on 
their borders where the climate was 
severe enough to be highly bracing, but 
not benumbing, there occurred an ex- 
traordinary development of — brain 
power. As evolution counts the years 
of Heredity 
we are still too near to see this develop- 
ment in its true light. Yet it can 
scarcely be mere chance that man rose 
above the animals during a great glacial 
period such as that which directed the 
wonderful evolutionary changes of the 
far earlier Permian Period. 
“Still less is it likely to be mere 
chance that the evolution of the powers 
of the human brain was relatively slow 
until the last of the four great epochs 
into which the Glacial Period is divided. 
That last epoch was colder and more 
severe than any of the others. Close 
to the ice-sheets it was apparently so 
severe that it caused retrogression, but 
farther away it apparently provided 
conditions such that man changed a 
thousand times faster than the animals 
had changed during the vast periods 
of relatively uniform climate in earlier 
geological times. . . . Clearly a severe 
climate is wonderfully potent in hasten- 
ing the course of evolution.” 
SEEKING AN EXPLANATION 
This last conclusion would doubtless 
be accepted by all biologists, since a 
rigorous climate means an intensity of 
natural selection that perpetuates 
favorable variations. But Dr. Hunting- 
ton seeks a more direct intervention of 
climate in evolution and devotes a chap- 
ter to “New Types among Animals,” 
in which he argues that the effect of 
climatic changes is to induce sudden, 
inheritable mutations. 
This, of course, is an old stamping- 
ground for biologists, and they will not 
consider that he has made out a strong 
case; nor does he claim that the evi- 
dence is now conclusive. He bases his 
hopes on a few well-known  experi- 
ments stich as: (1) the effects of 
changes of temperature on the pupae 
of butterflies; (2) W. L. Tower’s 
work on potato-beetles; (3) experi- 
ments on drosophila under extremes of 
temperature; (4) P. Kammerer’s work 
on toads; (5) F. B. Sumner’s experi- 
ments with mice; and (6) A. H. 
Clark’s observations on crinoids from 
different regions. Some of these ex- 
