"By all odds, earliest man, so naked to the elements and to deadly enemies, should have existed in a state of constant shock. We find him instead the only lighthearted being in a deadly serious universe.... He alone, with childish carelessness, tinkered and played, and exerted himself more in the pursuit of superfluities than of necessities. Yet the tinkering and playing, and the fascination with the nonessential, were a chief source of the inventiveness which enabled man to prevail over better-equipped and more-purposeful animals."