SOMETIME later this year a three-ton slab of bluestone will complete a 240-mile journey from Mynachlogddu, in western Wales, to the ring of Stonehenge, on Salisbury Plain, in Wiltshire, England. Mynachlogddu is where some of Stonehenge's raw material is thought to have been quarried, 4,000 years ago, and archaeologists have proposed various theories to explain how the megaliths were transported. The current journey -- a demonstration of one of these theories -- involves a wooden sledge, runners made of tree trunks, two replicas of a Neolithic currach, a lot of rope, and teams of volunteers working in shifts (but not in animal skins). The volunteers began their exertions last April, dragging the bluestone slab about a mile a day for several weeks. At Milford Haven the megalith embarked by water for England. It sank and was recovered, and the journey resumed. By the time the slab gets to Stonehenge, the teams will have invested some 30,000 man-hours in the endeavor. "We still don't know exactly how they did it," a spokesperson for the organizing group explained, referring to the ancient Britons who somehow moved the megaliths. She added, "We will only be using information available at the time."
The Mynachlogddu-to-Stonehenge trek continues a long tradition of experimental archaeology, with intrepid researchers exploring historical mysteries and putting speculative solutions to the test. Admiral Samuel Eliot Morison, a skilled navigator, sought to reconstruct the voyages of Columbus. The Norwegian adventurer Thor Heyerdahl ventured out in leaky facsimiles of primitive vessels to demonstrate the seafaring capacities of ancient Polynesians and Egyptians. Today, in quieter corners of academe, scholars try to duplicate lost techniques of farming and manufacturing and craftsmanship.
Such projects may vary in value, but overall they serve as a pointed reminder of just how much seemingly basic information about the past has somehow disappeared. The exact recipe for the mortar used in the pyramids remains a matter of debate. So does the age of the Sphinx and the cause of the death of King Tut (he may have been murdered). There is no agreement on whether the ancient Greeks and Romans read silently to themselves, or only aloud. Those famous Paleolithic figurines of Rubenesque women: are they fertility icons carved by men or self-portraits carved by pregnant women? Both schools of thought have forceful advocates. Which came first, the domestication of the horse or the invention of the wheel? Did Homo erectus have language or the control of fire? Did some real calamity provide a basis for the biblical story of the Flood? The answers to all of the above are in dispute.
And these are just the narrow, focused questions. The maw of our ignorance yawns pitilessly when it comes to bigger issues, such as why Rome fell, or what feudalism really was, or how capitalism came to develop.
All of which prompts one to wonder: will our own time be any easier for historians to puzzle out? The written records we leave behind will be far more abundant, although interpretation will be as much of a problem as ever. Some sources, reliably untrustworthy for years, may suddenly veer off in confounding directions. (The proprietor of the National Enquirer recently vowed to make his newspaper "a credible news-gathering force where everything you read is absolutely true.") Other sources, though factually scrupulous, raise more questions than they settle. (One can only guess what future scholars will make of the notice inserted into copies of Richard Neville's memoir Hippie Hippie Shake: "Erratum: page 71, line 4.... Germaine Greer has had a natural menopause and is still in possession of her uterus.")
But the biggest obstacle to understanding the present world is likely to be its sheer jumble. Historians and archaeologists need a certain amount of coherence in the landscape of the past. Caprice causes mischief. For years nailing down the date and location of the origin of chess was stymied by an archaeological conundrum. Experts had long believed that chess was invented in Asia in the sixth century, but this conclusion was cast into doubt by the discovery, in 1932, of a set of ivory chess pieces in a grave in Italy dating back to the third century. Six decades passed before radiocarbon dating established that the chess pieces were probably of tenth-century manufacture, reviving the original theory. How the pieces found their way into that third-century grave remains a mystery.