Two sources explore the invention and impact of wheeled vehicles. One source notes the earliest appearances of wheeled vehicles around 3500 BCE in various regions. The second source, a scholarly article, details the invention's profound effects on trade, specialization, and warfare, also highlighting parallel innovations like animal domestication and road construction. The article presents evidence from various sites and cultures, examining different wheel types and their evolution. Finally, the article discusses the debate surrounding whether the wheel's invention was a single event or multiple independent occurrences.