The picture illustrates how cutting tools in the Stone Age had developed, with tool A dating 1.4 million years ago, and tool B 0.8 million years ago.
Overall, tool A was much rudimental, with its edges being less defined, and therefore less sharp, and tool B’s surface was less rugged and it was larger and longer than that of its earlier counterpart. Both improvements allowed people to hold it more easily and enhanced its cutting functionality.
Tool A was about 9cm long, which was approximately 2cm shorter than tool B. The front and back views of both tools reveal that the latter’s surface was much soother, and its pointy shape resembled a waterdrop, making it easier to hold at the bigger end and more efficient in piercing food.
The side view clearly indicates that the thickness of both tools was the same. However, the well-defined line running from the top to the bottom of the picture means tool B had become much sharper.