Tools also provide evidence for human evolution. Primitive tools (flint hand axes) have been found in remains from the Palaeolithic Age (10,000 to 2.5 million years ago). More advanced tools (arrowheads) have been found from the Mesolithic Age (6,000 to 10,000 years ago), and even more advanced tools have been found from the Neolithic Age (4,000 to 6,000 years ago).
These dates are only approximate, as the tools have been dated from the environments they were found in. This is often the layer of sediment that surrounds the tool. Dating can be done by radiocarbon dating or other techniques which look at the amounts of elements like iron or potassium. It is the assumed that the tool is approximately as old as the rock which surrounds it.