In the early 19th century the Danish antiquarian CJ Thomsen devised a system for studying prehistory (the time before written records) by dividing it into three periods which he named the Stone Age, the Bronze Age and the Iron Age.
Thomsen’s Three Age System is still used today. However, within only a few decades of Thomsen devising it, new archaeological evidence had shown both that the Stone Age extended far further back in time than had previously been thought, and that there were distinct phases within it. The British archaeologist John Lubbock therefore proposed a further subdivision of the Stone Age into what he termed the Palaeolithic and Neolithic, or the Old Stone Age and the New Stone Age. Shortly afterwards the Irish archaeologist Hodder Westropp suggested yet another subdivision to describe a period between the Palaeolithic and the Neolithic which he termed the Mesolithic, or Middle Stone Age. The beginning of the Palaeolithic about 2.5 million years ago is marked by the appearance in the archaeological record of the first stone tools. The appearance of more finely carved tools and blades to make tools and weapons, particularly hunting spears, is now taken to mark the end of the Palaeolithic and the beginning of the Mesolithic, which in Europe and southwest Asia took place around 20,000 years ago.
The event which divides the Mesolithic from the Neolithic is the domestication of wild cereals, sometimes referred to as the invention of agriculture, which seems to have taken place in southwest Asia about 12,000 years ago. This also marked the beginning of the end of hunting and gathering as a way of life for the vast majority of cultures which had been pursued by modern humans since we first appeared as a distinct species about 200,000 years ago.