The provided photo describes a man-made stone cutters in two dissimilar periods in the past, namely Tool A and Tool B.
Overall, the tool in the latter period was sharper and bigger than its previous version.
During the early period, about 14 million years ago, the tool was rough with a large amount of blur. Both the front view and back view contained various shapes, and the top was not sharp. The whole tool was quite a small multi-angle stone block.
Turning to the later era, about 800,000 years ago, the cutter was revolutionized to become sharper on the top. At that time, the rough angles were adjusted, leaving a smooth shape from the bottom to the head. From the side view, the whole cutting tool was big in the middle and gradually narrowed until its peak, compared to the widened top of that in the early period.