Archaeology is self-scrutiny. The unreflecting person clumps about on the earth's surface, but if she needs to know more about who she is and where she came from, she must dig down. As a compulsion it is modern: Jennifer Wallace, in her profound and fascinating new book, Digging the Dirt, locates its beginnings in figures such as William Stukeley, whose lively, some said fantastic, explorations of Avebury and Stonehenge in the early 18th century began the work of fleshing out our remote ancestors.
What we find when we dig down depends on where we dig. If, like the luckless and idiotic 18th-century barrow-diggers we spend pointless years ransacking one empty barrow after another, the answer is nothing much. If, on the other hand, we are astute and lucky like Heinrich Schliemann at Mycenae in Greece, we may come across the mask of "Agamemnon", with the face underneath it preserved for a few magical seconds before crumbling into dust.
Man has always left his rubbish behind him, and in time the earth has always blown over it and interred it. There is a pleasing solidity and objectivity about the subject, in contrast to other more slippery ways of investigating the past. Bit by bit the relics emerge. But what do we do with them once we have dug them up? What do they mean once we have brought them "owte of deadely darknes to lyvely lighte" (as the 16th-century proto-archaeologist John Leland put it)?
As Wallace, a Cambridge English don when she is not up to her neck in rubble, brings out, there are many different ways both to use and abuse the fruits of excavation; and even the most pious or scholarly endeavours have a way of lurching into something less respectable. Robert Burns's head was dug up for phrenologists to examine, for clues about his poetic genius. But before being replaced it was tossed from hand to hand by the diggers, as they tried their hats on it to see which fitted.
A century after his death, John Milton's body was dug up by his admirers to establish its precise location, so the monument they planned to erect would be in the right place. But after a few pints the diggers returned to the corpse, and grabbed teeth and hanks of Milton's hair for souvenirs. Next day the corpse's guards began charging locals to have a butchers at the great man, now a revolting mound of slime. Meanwhile "outside the church, the men were cutting up Milton's bones and hair into smaller pieces and selling them on the black market."
Some of the world's most famous digs are beset by dark ambiguities. Schliemann, the German who claimed to have gazed on the face of Agamemnon, dedicated much of his life to establishing the historical basis for Homer's epics. But the deepest motive for his quest, Wallace writes, was to establish the continuity of Aryan blood from ancient Troy to modern Germany. The "proof" of the theory, which fed directly into the ideology of Nazism, was the alleged continuity of the swastika symbol.
At Pompeii, the most arresting discovery was the buried city's huge collection of erotic artefacts. When William Hamilton, British ambassador in Naples, gave a talk on Pompeii to London's Society of Antiquaries, what the assembled gents were really interested in was the smut. "As the worthy antiquarians sat electrified in their elegant headquarters," Wallace writes, "Hamilton created for them a masterpiece of tease, hinting at obscenities while denying them at the same time..."
Yet what such crassness fails to dispel is the mystery of our encounter with the past. It is a descent into the underworld, and for those who visited Pompeii or Herculaneum in the mid-18th century, when the only access to the ancient houses and streets was through tunnels and mines, that was what it looked like. "The sketch of Alcubierre's excavation of Herculaneum," Wallace writes, "... reveals an almost Dantean vision of the entry into the Inferno. Some men stand on the cliff's edge at the top, presumably in the daylit, rational level of the 18th century, while other men beaver away with wheelbarrows of earth ... Meanwhile other men hang over the edge, staring down into the abyss..."
For Freud, who had a lifelong obsession with antiquities, a city like Rome, where new buildings jostle ruins 2,000 years old, was a depiction of the human mind, where "nothing that has once been formed can perish - everything is somehow preserved and in suitable circumstances can once more be brought to light."
At the heart of the archaeological experience is the encounter, in persons long dead or the places they inhabited, with ourselves. "Once every few months," she writes, "I go to visit the bog man in the British Museum. ... it is little more than a mass of leather and bones, just half a torso and one lower leg ... when I visit him, on a regular basis, I linger over the glass case, marvelling at the perfectly formed left ear, the hair plastered down on his head and the brown skin drawn tight over his sharp cheek bone, and I am awed into a type of reverence."
Why? "What should be dead," she writes, "appears to be alive ... Nature and time might not be as reliable as one previously thought. Surprised by an unexpected re-occurrence or re-emergence of something one thought to be safely buried in the past, one experiences, in the words of the critic Nicholas Royle, 'a disturbance of any sense of 'familiar ground'."
Archaeology, like everything else, is speeding up: new technologies enable archaeologists to penetrate to places they have never been before, sending robots to the sea bed to explore the wreck of the Titanic, making possible deep penetration into ancient Mayan tunnel systems to view victims of human sacrifice. At the same time, post-modern narcissism turns the gaze compulsively back on ourselves and what we throw out: one of the newest branches of archaeology is "garbology", with researchers sifting through immense landfills like Fresh Kills in New York.
More data, then, telling us more and more about less and less, because, as Wallace quotes Frederic Jameson, "since everything now submits to the perpetual change of fashion and media image, nothing can change any longer."
In the context of which, the mysteries Wallace celebrates seem even more precious: the "uncomfortable intimacy" afforded by the bogman; the figures of victims of Pompeii that were created by pouring plaster of paris into the holes left in the solidified ash by the victims before they decomposed, human beings who are simultaneously present and absent, "making concrete the human life now lost".
To order a copy of 'Digging the Dirt: The Archaeological Imagination' (Duckworth £14.99) for £13.99 (free p&p) call Independent Books Direct on 08700 798897