The ages of human history

As a custom, historians divide eras of people according to the material from which they made their tools. The earliest tools were made of stone, and so we have the Stone Age. Then follow the Bronze Age and the Iron Age. More recently, a finer alloy of iron allowed greater expansion of industry, so we can refer to a Steel Age. Then, around the middle of the twentieth century, we entered the Plastic Age.

Here is a trick question: when does one age end and another begin? The question cannot be answered until we specify the area in question and even which group within that area. The Bible describes a time, when Saul was king of Israel, that the Israelites were in the Bronze Age while the Philistines were in the Iron Age. This gave the Philistines advantages over the Israelites—military advantages and agricultural advantages—because the Philistines were using better tools.

Each of these ages is further divided into various segments, often very detailed in their descriptions. Pottery, basket weaving, and other early industries help to define these segments; they also indicate when two or more groups of people exchanged items they had made. The larger ages are sufficient for a general discussion of history, although the Stone Age is generally divided. When I was younger, we learned about the Paleolithic Age, or Old Stone Age; and the Mesolithic, or Middle Stone Age, and the Neolithic, or New Stone Age. I never learned all the distinctions among the three stone ages, aside from the fact that the Paleolithic came first and the Neolithic is most recent. Now books only separate the Paleolithic and Neolithic ages. The distinction is easy: Paleolithic people have no set home; they travel to hunt and harvest their food. Neolithic people have settlements; they raise flocks and herds of animals, and they plant seeds and tend the plants that grow and harvest the crops when they are ripe.

Extremely useful tools are made from stones. Flint and obsidian are especially helpful because sharp blades can be chipped from these stones. Sharp stones became knives that cut food, axes that cut wood, and weapons that helped when hunting animals or when battling other groups of people for resources. Many North Americans have gathered what are commonly called “arrowheads.” Most of these shaped stones are too large for arrows; they were used instead on short spears that were thrown at a target, such as deer or bison. Professional historians and archaeologists classify these tools as “projectile points.”

Back to the trick question: speaking on a world-wide basis, the Paleolithic Age has never ended. Some people today still choose to live in a Paleolithic pattern. Not only are their tools made of stone; they travel to hunt and to harvest their food. They have no permanent settlements. They are aware of newer possibilities in civilization—bronze and iron and steel and plastic. They choose to perpetuate the ways of their ancestors. Australia, Siberia, and many other parts of the world are home to Paleolithic groups that preserve their ancient customs and choose not to adapt to newer ways.

No written records describe the discovery of bronze. Bronze is an alloy, a mixture of copper and tin. (Some parts of the world had a Copper Age before they entered the Bronze Age.) Copper and tin ores exist naturally in some rocks; historians assume that people who gathered rocks to line their fire pits found a new substance in the morning when the fires had gone out. This new substance, bronze, could be shaped more easily than stone. Bronze blades on weapons and other tools lasted longer than stone blades. The advantage of bronze tools made them the choice of most civilized groups that encountered them, either by their own discovery or through trade with other groups.  

Iron is even more durable than bronze. Iron does not melt in a normal fire, which is why many campers use cast iron pots and skillets. Pure iron is a powder, but a mixture of iron and carbon produces an alloy which is extremely useful. Once people learned how to blow air into a fire to make it hotter, they were ready for the Iron Age. The earliest appearance of that industry seems to have occurred among the Hittites, living in what now is the country called Turkey. The technology spread to neighboring civilizations. It appears to have arisen spontaneously in China and in central Africa as well. Iron technology caused a great gap between “haves” and “have-nots” in the ancient world. Some civilizations, including the Philistines, attempted to preserve a monopoly on iron technology, but they were only able to hold that monopoly for a few years, never for long.

About a thousand years ago, chemists in China found a new way of combining iron and carbon which made a finer version of iron, which we call steel rather than cast iron. Once again, this new technology offered advantages over the older iron tools. Gradually, this chemical knowledge moved along the trade routes called the Silk Roads, until it reached the British Isles in western Europe. The British had advantages which had not existed in China or in other civilizations on the Silk Roads: they had iron deposits, coal deposits, and running water for generating power all located near one another. Chinese inventors made the first water wheels—wheels turned by a flowing stream of water, generating power to operate machinery such as grain mills. Europeans improved this Chinese invention by positioning the water wheels vertically instead of horizontally in the streams of water. This allowed gravity to add to the energy of the moving water, generating even more power. The Industrial Revolution began in Great Britain a few centuries ago because of the use of these Chinese discoveries—the recipe for finer steel, and the power that comes from a wheel turned by water.

Now most of the tools we use are made, at least in part, from plastic. Plastic is made from petroleum, so people will need to continue mining and refining petroleum even if it ceases to be a source of energy to operate vehicles and to generate electricity. Plastic is extremely useful for tools, but plastic can cause more damage to the environment than stones or metal, since it does not exist as such in nature. People have shown in the past that we can be inventive, finding new materials to improve older technologies. Perhaps even now researchers in a laboratory somewhere are experimenting with a new substance that will replace plastic and move humanity into yet another age. J.