The Mesopotamian Civilization

We believe Sumerian civilization first took form in southern Mesopotamia around 4000 BCE—or 6000 years ago—which would make it the first urban civilization in the region. ... The incredibly important invention of the wheel is also credited to the Sumerians; the earliest discovered wheel dates to 3500 BCE in Mesopotamia.

References
1. Khan Academy [www.khanacademy.org]
2. ancient history lists [www.ancienthistorylists.com]