[rm30]

I wonder if the bow drill principle for boring holes evolved from fire-starting techniques, where the same reciprocal motion was already understood and mastered in that years.

Just speculation, but it suggests how practical problem-solving builds on existing techniques rather than appearing fully formed.

[Sharlin]

Given that humans must have "always" known that carving a hole in something is easier if you use your wrist to reciprocally rotate the tool, I'd be inclined to suspect that both hole-making and firestarting with a bow drill were invented more or less contemporaneously.

[MomsAVoxell]

Yes, but didn’t our wrists evolve because of all the fire-starting?