There were no longer any animals to be killed for food in the valley of the caves, and the people there gave up being hunters, and spent their time making things, such as pottery, stone implements of all sorts, weapons, leather, moccasins, and smoked meats and fish. They were the workers, while the tribes outside were the hunters and fishers. When any man in the outside tribes killed more deer, or caught more fish, than he needed, he would bring them to the people in the valley, and exchange them for spear heads, smoked meats, pottery, tanned leather, or any of the other things he needed. This was the very beginning of barter, or trade. When one tribe had more than they needed of one thing, and another tribe had more than they needed of another, they would exchange with each other, so that both were better off. This trading of things between peoples is what makes up the business of the world to-day. If the people in the United States have more wheat, or beef than they need, and the people in England have more leather goods, or cutlery, or woolen cloth, or the people in France more silks and satins, we send our wheat or beef, or cotton to them, and bring back their leather goods, or cutlery, or silk. In the beginning, it was very easy for a hunter to bring a bundle of skins, or a string of fish into the valley, and exchange it for what he needed, a stone axe, or a leather coat, or a pottery bowl. Later on, when the tribes of men had spread far over the country, it often happened that the hunter who brought a bundle of skins to one tribe, did not want to buy anything from that tribe, but instead, wanted to go to some other tribe, a long distance off, to get something they had which he particularly wanted. This made a difficulty, and to overcome it, something was needed that could be exchanged with any tribe, and yet could be easily carried about, on long journeys. So the people began to use beads, and later on, when metals had been discovered, ornaments such as bracelets, or rings made of copper, or gold, and these beads and ornaments became the first money used by man. But this came later on; now the traders exchanged one thing for another, just as they do in savage countries to-day. There were some grasses which grew in the valley, which bore tiny hard seeds or grains on their tops, and for a long time the cave people had made use of these grains for food, when other things were scarce. After a while, they noticed that if they let any of these grains fall in the soft earth, they would grow up again, and have more grains on them. They saw that this was an easy way to get food, so they took the grains and planted them, scratching up the hard ground with the points of their spears. Later on they made a tool something like a hoe, by fastening a sharp piece of stone crosswise at the end of a stick, and used this to loosen the ground for planting the grain.