Introduction to Archaeology
The earliest tools are simply pebbles which have been modified only to a limited degree. Either unifacially or bifacially worked, only a simple cutting edge is created.
Hand axes are an extension of the pebble tool technology. The worked area is extended down the body of the core.
Here are three sides of a Lower Paleolithic discoidal core tool. Note the remnants of the cortex still remaining on one of the tools's surfaces.
Here is an excellent example of core tools which reflects the long-term process of being hand axes being progressively worked further down the length of their body. Note the original unworked surface on the lower part of the tool.