Bodo had never had a warm dinner. He had no fire to cook his food. Much of his food was hard and tough. He had not learned to soften it with fire. He had not learned to crush or grind it with stones. His teeth did all of this work. The teeth of all the Tree-dwellers were large and strong. They were fitted to cut and grind tough food. They were fitted to crack the shells of nuts. Bodo often cracked nuts with his teeth. But sometimes he found nuts that he could not crack. He had never seen or heard of a hammer, so he threw a hard nut against a rock. The nut did not crack. So he kept on trying different ways. At last he struck the nut with a stone. Its hard shell broke. How glad Bodo was! He ate the kernel and then cracked some more nuts with the stone. This stone was his first hammer. Sometimes he used a rough stone. Its rough edges hurt his hand, so he hunted for a smooth stone. At other times he wrapped one end of a rough stone in grass. The grass protected his hand. This was the first handle to his hammer. Bodo liked to use this hammer. He liked to use smooth hammer-stones. But sometimes the smooth stone slipped or bounded back and jarred his hand. [Illustration: "_Bodo cracked nuts with a stone_"] One day he found a smooth stone that had a little pit on either side. He put his thumb and finger into the pits and cracked a hard nut with the stone. This was just what he needed. It neither slipped nor jarred his hand. Some of the other Tree-dwellers tried it. They wanted one like it, so they began to hunt for pitted stones. They could not always find such stones, but they never thought of making the pits. People lived many years before they learned to do that. Tree-dwellers simply used things that they found on the spot. [Illustration: _The chipped pebble_] They seldom changed their shape. We have only a few weapons that we know they made. They were found years ago deep down in some gravel. They had lain there many long years. Here is a picture of one. It is only a chipped pebble. Such a weapon is used nowadays only in play, but then it was used in real work. For a long time the Tree-dwellers did not have even this. They used their teeth and nails instead. [Illustration: _An antler used as a wedge_]