Ancient Sumer may have been the first civilization to start adding tin to copper to make bronze. Bronze was harder and more durable than copper, which made bronze a better metal for tools and weapons. Archaeological evidence suggests the transition from copper to bronze took place around 3300 B.C. The invention of bronze brought an end to the Stone Age, the prehistoric period dominated by the use of stone tools and weaponry. Different human societies entered the Bronze Age at different times. Civilizations in Greece began working with copper and tin to make bronze before 3000 B.C., while the British Isles and China entered the Bronze Age much later—around 1900 B.C. and 1600 B.C., respectively.

Source: History Channel