e was less abundant than in his old, and the
instigation to agricultural pursuits was stronger. And though Europe was
thickly wooded, it probably presented more open land than Africa. Both
the incitement to agriculture and the facilities for its exercise were,
in all probability, greater than in Africa, and man may have begun to
cultivate the earth here at an earlier date than in his native realm. We
are free at least to speculate that European man gained some slight
knowledge of agriculture in the pre-glacial period, but this is
doubtful, and the relics of early man yield no evidence in its favor.
Mentally it is questionable if he was advanced beyond the level of the
least developed negro tribes, and perhaps not beyond that of the forest
pygmies.

But at length the shadow of a mighty coming change began to fall upon
the fair face of Europe. Year by year the winters grew colder. The ice
sheet, which was in time to bury half of Europe under its chilly mantle,
had begun its slow movement toward the south. It advanced very slowly.
Centuries elapsed during its deliberate march. Had it moved with
rapidity, few animals could have survived its effects. Some of them
found time for changes in structure to fit themselves to the new
conditions. Others perished as the wintry chill increased. Constituted
for tropical warmth, they were unable to endure severe cold. The apes
and monkeys may have been among the early victims. To-day the apes of
Gibraltar are the only ones existing in a wild state in Europe, and it
is doubtful if they are of an original stock. There is good reason to
believe that escape by migration southward was cut off by the sinking of
the ancient land bridges, so that the animals north of the Mediterranean
had no choice between adaptation and annihilation.

Among the animals thus taken prisoner by the glacial chill was European
man. He could not escape, and was forced to remain, exposed to the
alternatives of perishing from cold and hunger, or fitting himself to
endure the new conditions which were coming upon his northern home,
perhaps the most adverse to animal life that had ever been known. Man
was about to be subjected to an extraordinary strain, which he could
only meet by an extraordinary adaptation.

The changes by which he met these new conditions were in a very small
degree physical; they were almost wholly mental. In all animals of the
higher orders, adaptive variations are apt to be in a measure of this