common shape is a pointed area at one end, cutting edges along its side and a rounded base (this includes hand axes with a lanceolate and amygdaloidal shape as well as others from the family). The axes are almost always symmetrical, despite studies showing that symmetry doesn’t help in tasks such as using a hand axe for skinning animals. While there is a “typical” shape to most hand axes, there are some displaying a variety of shapes, including circular, triangular and elliptical—calling in to question the contention that they had a constant and only symbolic significance. They are typically between long, although they can be bigger or smaller. They were typically made from a rounded stone, a block or lithic flake, using a hammer to remove flakes from both sides of the item. This hammer can be made of hard stone, or of wood or antler. The latter two, softer hammers can produce more delicate results. However, a hand axe's technological aspect can reflect more differences. For example, uniface tools have only been worked on one side and partial bifaces retain a high proportion of the natural cortex of the tool stone, often making them easy to confuse with chopping tools. Further, simple bifaces may have been created from a suitable tool stone, but they rarely show evidence of retouching. Later hand axes were improved by the use of the Levallois technique to make the more sophisticated and lighter Levallois core. In summary, hand axes are recognized by many typological schools under different archaeological paradigms and are quite recognisable (at least the most typical examples). However, they have not been definitively categorized. Stated more formally, the idealised model combines a series of well-defined properties, but no set of these properties are necessary or sufficient to identify a hand axe. History and distribution In 1969 in the 2nd edition of World Prehistory, Grahame Clark proposed an evolutionary progression of flint-knapping industries (also known as complexes or technocomplexes) in which the "dominant lithic technologies" occurred in a fixed sequence where simple Oldowan one-edged tools were replaced by these more complex Acheulean hand axes, which were then eventually replaced by the even more complex Mousterian tools made with the Levallois technique. The oldest known Oldowan tools were found in Gona, Ethiopia. These are dated to about 2.6 mya. Early examples of hand axes date back to 1.6 mya in the later Oldowan (Mode