All the plants died. The animals fled in search of the southern sun. The
valley became uninhabitable. Man hoisted his children upon his back,
took the few pieces of stone which he had used as a weapon and went
forth to find a new home.

Why the world should have grown cold at that particular moment, we do
not know. We can not even guess at the cause.

The gradual lowering of the temperature, however, made a great
difference to the human race.

For a time it looked as if every one would die. But in the end this
period of suffering proved a real blessing. It killed all the weaker
people and forced the survivors to sharpen their wits lest they
perish, too.

Placed before the choice of hard thinking or quick dying the same brain
that had first turned a stone into a hatchet now solved difficulties
which had never faced the older generations.

In the first place, there was the question of clothing. It had grown
much too cold to do without some sort of artificial covering. Bears and
bisons and other animals who live in northern regions are protected
against snow and ice by a heavy coat of fur. Man possessed no such coat.
His skin was very delicate and he suffered greatly.

He solved his problem in a very simple fashion. He dug a hole and he
covered it with branches and leaves and a little grass. A bear came by
and fell into this artificial cave. Man waited until the creature was