Rope, twine and thread: Invisible technologies of the Stone Age

Not mentioned in TFA: cordage is a critical component in slings, an early, powerful ranged weapon.

With some sort of pulley, rope allows a single human to excert large amounts of force trough leverage, often in ways more convenient than other forms of mechanical leverage. (Such as actual levers.)

Rope can also be used for 1:1 power transfer.