Man's ancestors were living in trees. The quadruped creature became biped. Two of the paws developed into hands and enabled him to swing from branch to branch. His head became upright, his body tended to the vertical position, and his brain grew in volume.

A further miracle remained before this primate became a human being. This miracle, no doubt, lies in the Ice Age which uprooted the forests  and left a few droves of anthropoid monkeys isolated at the feet of the mountains, deprived of their habitat (trees), and forced to seek a new life in the security of caves threatened in their hiding places by bears and lions. The only choice before them was to fight or vanish utterly. They had neither paws nor tusks but the self-preservation instinct supplied them with a weapon that above all price – i.e. intelligence.
 
At that moment, man was born. He was naked in a hostile world. But the means of assuring his future triumph were within his reach. Like a child in its cradle, he had at his disposal the potential of that intelligence which was to enable him to establish his dominion in a world which ill-received him. He began to assure his supremacy over all beasts of prey from which he escaped. How, but for the gift of thought, could he resist them? That gift was his sole weapon, a matchless weapon.
 
Man started from scratch. He had to invent everything and discover everything beginning with his own body, and the planet which he called his home. The hoarded treasure of his knowledge and technical skill was enhanced from generation to generation in spite of occasional periods of relapse. He was able to transmit this, and it is this which we call civilization. No other species of the animal world seems able to enlarge his store of the acquired knowledge. Man, alone, since the dawn of his history, directed his gift of indestructible intelligence to the task of enriching his cultural heritage infinitely.