Being terrestrial is one obvious requirement. No fully aquatic species could master fire and thus develop metallurgy.
If the conductivity of copper were ten times less, wires would have to be ten times the cross-sectional area to provide the same conductivity.
As we have seen so far in this series, fire was an absolutely crucial component in humanity’s rise to civilization and technology.
The combustion of wood or coal may seem so familiar as to be unworthy of any comment.
Of all the discoveries made on mankind’s long march to civilization, there was one primal discovery that made the realization of all else possible.