The illustration details the evolution of cutting tools used by men in the Stone Age throughout two periods. As observed, the key difference between these cutting tools is the size, with latter version becoming significantly larger. Furthermore, tool B shows more refined appearance than tool A regarding sharpness and shapes.
1.4 million years ago, the cutting tools were thin, measured 5-7 centimetres in length, and did not display any craftmanship. The appearance was uneven as the front and the back were shaped differently and the surface was quite rough.
600 years later, the cutting tools used by the prehistoric men in the Stone Age become noticeably more advanced. Firsly, it appeared considerably larger, measuring 10-11 centimetres in length, and had a more defined tear-drop shape: fat at base and taperring agressively towards the tip whereas the prior version was quite obtuse. Secondly, the front and the back were ground evenly and smoothly.