Paved roads

The paved road did not emerge from abstract planning. It emerged from mud—specifically, from the failure of natural surfaces to support wheeled transport in the wet season. The cities of Mesopotamia, where the wheel was already transforming commerce around 3500 BCE, could not realize its potential until they solved the problem of ground that turned to impassable mire whenever rain fell between the Tigris and Euphrates.

The oldest constructed roads discovered to date are in former Mesopotamia, now Iraq. Stone-paved streets in the cities of Ur and Babylon date to approximately 4000 BCE—coinciding almost exactly with the emergence of wheeled vehicles and cuneiform writing. This was not coincidence. Wheels create demand for surfaces hard enough to bear their loads. Writing enables the coordination required to mobilize labor for infrastructure. The three technologies formed a reinforcing triad: wheels made roads valuable, writing made roads buildable, roads made wheels useful across distances.

The Sumerians constructed their roads from materials that varied by availability and purpose. In urban areas, they formed identical mud bricks, dried them in the sun, and set them into place with bitumen—the sticky black petroleum residue that seeped from natural deposits throughout the region. This bitumen, the same substance used in modern asphalt, made Mesopotamian roads ancestors of the highways that now circle the planet. The Babylonians used similar techniques, while areas with available stone employed dressed blocks.

The adjacent possible for paved roads required several preceding developments. First, the wheel itself—a 1,000-pound oxcart cannot travel far on packed earth before its wheels sink or ruts form. Second, urbanization—scattered villages need only footpaths, while cities require surfaces that can bear commercial traffic. Third, centralized authority—roads are public goods that benefit everyone but require collective resources to build. The temple administrators and early kings who mobilized labor for roads were investing in infrastructure that would amplify their own economic and military reach.

The strategic logic was inescapable. By 4000 BCE, paved roads in Ur and Babylon were being constructed explicitly to carry armies as well as trade. A soldier on foot covers roughly 20 miles per day on good surfaces, half that on muddy trails. A chariot or supply wagon faces even starker arithmetic. Roads didn't just enable movement—they accelerated it, and acceleration compounds into military advantage.

The coincidence of paved roads and cuneiform writing is telling. With an expanding culture and community came the necessity for communication, and both roads and the written word made communication faster and more effective. Roads made alliances with neighboring kingdoms and their armies possible; writing made treaties enforceable across distance. The two technologies reinforced each other's value.

The cascade from Mesopotamian road-building extends through every subsequent empire. Persian Royal Roads, Roman Via networks, Chinese highways, British turnpikes, and American interstates all elaborate on the same fundamental insight: a hard, durable surface connecting points A and B transforms both locations by reducing the friction of distance. The mud-brick streets of Ur are ancestors of the asphalt ribbons that now span continents.

By 2026, paved roads cover over 64 million kilometers worldwide—enough to wrap the Earth 1,600 times. The fundamental challenge Sumerian engineers faced 6,000 years ago persists in new forms: surfaces that can bear increasing loads, resist weathering, and channel traffic efficiently. The materials have evolved from mud brick to concrete to smart surfaces embedded with sensors, but the essential problem remains unchanged: wheels need ground that does not yield.