### Instruction: When was the wheel invented?
### Response: No one knows when the wheel was first made. Archaeological evidence seems to show that the wheel was first used to make pottery in Mesopotamia about 7,000 years ago, during the Neolithic period. Later, it was used to make chariots. Chariot wheels have been found in Sumer as early as 3000 BC. The wheel is one of the most important inventions in human history. It was very useful for making pottery and getting around on land. It is also a key part of machines.