The pictures describe the evolution of Stone Age cutting tools between 1.4 million and 0.8 million years ago. It can be seen that the latter design had seen vast improvements in the size, shape and finishing quality.
Tool A, which dated back to 1.4 million years ago, was rather small and rudimentary. At about 7cm in length, the tool was thin and did not display much craftsmanship. The front and back view were plain with only some slight chiselling effort while the side was rough and not very indicative of a cutting utensil.
Tool B showed many updated features compared to the older version. First of all, it was larger and sturdier due to a better water drop design with a broad base and pointy top. Second, both front and back sides were grounded more evenly and smoothly. Finally, although the tool’s thickness stayed relatively the same after 0.6 million years, the side edge was undoubtedly much more finely sharpened.