The diagram illustrates the evolution of cutting tools from different eras of the Stone Age.
Overall, Stone Age cutting tools experienced a significant transformation from a rudimentary and asymmetrical fragment to a more sophisticated piece of stone over the given period.
Dating back to 1.4 million years ago, the cutting tool was crude and irregular in dimensions. In particular, its front view and back view were unevenly shaped with a broad base narrowing towards a blunt point whereas the side view demonstrates substantial thickness and a blunt edge, its length being approximately 8–9 centimeters.
In the following 0.6 million years, this kind of tool underwent an improvement in its complexity and refinement, with a primitive teardrop shape combined with a smoother texture. Its front view was more symmetrical and streamlined despite several haphazard flaking patterns. Additionally, the side view depicts better-refined edges, reflecting greater sharpness, and the back view had its width and height increased to acquire a balanced shape.