a very interesting way of digging - putting a stone weight higher up the handle rather than using a sharpened stone to pierce the ground. Did they use both methods?

The resilience of humans, knowing the earth untouched by the sun might be damp or contain buried tubers.

The use of sand as grit has long been used by ancient peoples and may have been used in Egypt with copper saws to make longitudinal cuts. Amazing how abrasive sand can be even when ground with a stick handle