In short, we experimented in modern times with stones that would have been readily available to pre-history humans and made shapes in the form of axes and other tools. Using that as a template, we can tell what are tool-marks and what is natural breakage.
This is a popular research topic, we examine tool marks from ancient human civilizations with recorded history because things like the pyramids seem…improbable, for the time and place. By studying the marks left by the tools used in construction, we can figure out the process they used to make things that are still around today. Using what they have learned, we can examine prehistory artifacts and get a good idea of how they were chipped into shape.
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