I wonder if they had meetings or 'design committees' to find the most optimal shape with respect to the ease of killing prey eventually.
One possibility on origin (totally made up by me) could be that there were large stones lying around already as debris from e.g. earthquakes, celestial events and such and some groups took advantage of this and later people iterated upon it.
One possibility on origin (totally made up by me) could be that there were large stones lying around already as debris from e.g. earthquakes, celestial events and such and some groups took advantage of this and later people iterated upon it.