Early humans made tools from stone, and these survive for millions of years. They give evidence about how our ancestors lived and how their skills developed.
The oldest stone tools are simple. They are roughly chipped stones used to cut meat or crack bones. Over time the tools became more complex. Later tools were shaped more carefully, with sharper edges and a more regular form, and some were made for particular jobs. Making them needed more skill and planning, which fits with ancestors developing larger brains.
Stone tools can be dated from their environment. Tools are often found buried in layers of rock. Deeper layers are usually older, so tools found lower down are older. Where a layer of volcanic ash lies in the rock, the age of the ash itself can be worked out by radioactive dating of the minerals in it. Other materials found with the tools, such as fossils and charcoal, can also be dated.
