I want to know the answer to the following question:
What started about 4000 years after copper smelting was discovered?
All the background I'm provided with is that "Alloying copper with tin to make bronze was first practiced about 4000 years after the discovery of copper smelting, and about 2000 years after "natural bronze" had come into general use[citation needed].". Is that enough to answer the question?
Answer: yes