The three ages system of archaeology works by dividing human prehistory (the time period before written history evolved) into three distinct ages, based on the technological advances civilization made. The civilizations best categorized as such are European and Mediterranean; however, other civilizations are sometimes described using this system too.
The three ages are dubbed the Stone, Bronze and Iron Ages. The Stone Age is further divided into three time periods: the Paleolithic, Mesolithic, and Neolithic ages.
The most primitive tools were invented in this time period. Generally, they were shaped (or chipped) from stone, wood and bone. We presume that leather and vegetable fibers were also used, but not many examples have been preserved. Clubs, hand axes, needles, and harpoons are a few examples. People lived in caves and huts, generally in bands of 25-100 hunters and gatherers. When a source of food moved, people were forced to move too. Spiritual activity such as ancestor worship and burials began, and art was created.
Tools became a little more complex as people learned to shape their surroundings with other tools. Boats were carved, and bows and arrows shaped to make the task of hunting a little easier. While the lifestyle was still largely mobile, the hunters and gatherers formed larger tribes and bands. One of the first known battles was fought in this time period, near modern-day Sudan, perhaps over a diminishing of natural resources in the area.
The complexity of tools was already improving in this time period. Chisels, ploughs, pottery, and more advanced weapons were created. As the ability to survive in one place grew, people began to live in farmsteads rather than move around as necessitated by the plant growth and animal movements. Fishing became more refined, and animals were now domesticated to make living in one spot easier. Large-scale construction of buildings, such as Stonehenge and Jericho, began around now. People still lived in tribes, but began to form chiefdoms towards the end of the period.
As metal refinery began, tools were shaped from copper. Then, copper and tin began to be smelted and combined into the stronger bronze. Pottery wheels were also invented. People still lived on farmsteads, and took up agriculture more than hunting and gathering now. They continued the process of domesticating cattle, and the trades and crafts began to form. In some advanced cultures, cities and states began to form, but for many, the Iron Age ushered in these changes. This age does not exist in some civilizations, who skipped directly from the Neolithic period to the Iron Age, and in other civilizations, extensive written records were kept already.
Tools were shaped from iron once this more versatile and common metal was discovered. People began to rely more on others as the crafts formed, realizing that it was more efficient to trade skills and time rather than try to survive doing everything in smaller groups. With this knowledge, cities and states began to form. This is the last period in the three ages system of archaeology, however, there is no defined point at which it ends and history begins.
For most civilizations, the end of the Iron Age is simply when the written records and surviving traditions become more important than archaeological evidence.