Today, we walk a six-thousand-year-old highway. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Roman roads loom large in legend and song! We forget there was ever anything before them. But archaeologist John Coles tells about a strange road, far older.

In 1970, Raymond Sweet was cleaning drainage ditches in a peat bog near Bristol, England. Deep in the peat, he struck a wooden plank. It was the wrong thing in the wrong place. He took it to Coles at Cambridge University. Coles dated it at 4000 B.C. A major dig was begun, and the full story began to come clear. The trail of wood went on and on, from what had been one island in the fen to another -- over a mile away.

The wood was well preserved. This strange structure had been used for a generation. Then reeds closed in, and peat quickly formed over it. The peat was acidic enough to kill the bacteria that degrade wood. As archaeologists uncovered it, the shape of the thing emerged.

Six thousand years ago, Neolithic engineers needed to get back and forth across the swamp below their village. They contrived a long walkway. First they laid a mile-long rail of four-inch-diameter poles on the underwater soil. Then they pounded five-foot pegs into the ground at a 45-degree angle. These pegs criss-crossed over the poles. They formed X-shaped brackets every few feet. The poles carried their weight. Finally wide planks were fitted into the upper arms of the X. The planks formed a walkway a foot above the water.

It was quite a piece of work for people still in the Stone Age. The children of these engineers would build Stonehenge nearby, but not for another two thousand years. Tool-marks on the wood show a fine command of carpentry. These boards were formed by people with better tools than we would have guessed. It took a very sophisticated wood-splitting technique to make those planks. Excavation even turned up surveyor's stakes that'd been used to lay out the path for its builders.

There's more. Artifacts dropped along the walkway show that these not-so-primitive people made pottery, that they'd invented glue, and that they traded with distant tribes for flint. The most startling artifact is an axehead shaped from European jade. These forgotten people clearly owned some mysteries that will remain mysterious.

But, most important, this path reveals social cohesion. It tells us that these ancestors could put their wills and minds together and produce a huge unique project for the common good -- six thousand years ago.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Coles, J.M., The World's Oldest Road. Scientific American, November 1989, pp. 100-106.

This episode has been greatly revised as Episode 2584.