The skull doctors
Reprinted from New Scientist vol 167 issue 2256 - 16 September 2000, page 32
Cruel torture, crude surgery or a mind-altering experience? Why would anyone have a hole drilled in their head, asks Stephanie Pain
AMANDA FEILDING put on her old white party frock, cut the hair away from her forehead and drilled a hole through the front of her skull. It was 1970, and 27-year-old Feilding had spent four years looking for a reputable surgeon who would perform the operation. Eventually, she gave up and did it herself.
Equipped with a dentist's electric drill operated by a foot pedal, she practised on an old skull before taking the plunge through her own bone. She taped dark glasses to her face to stop the blood running into her eyes, made an incision with a scalpel, then drilled, dipping the drill bit in water every so often to cool it down. "It seemed to take an amazingly long time," she says. She lost almost a litre of blood and ruined her party frock, but she was pleased with her DIY surgery. Feilding believes that trepanation—the removal of a piece of bone from the skull—heightens consciousness by giving the brain a little extra space to swell and subside with the beat of her heart, the way it does in infants before the skull bones knit together. "Over the next four hours I noticed myself rising up with a feeling of elation and relaxation," Feilding says. "I went out and had steak for supper, then I went to a party."
A thousand years earlier, in the central highlands of Peru, a young man lay unconscious, his skull cracked by a well-aimed slingshot. Splinters of bone were pressing into his brain. The village healer knelt down beside him, took out a new stone knife and made an incision in the scalp. Folding back the bleeding skin, he began to scrape at the bone, working in a circle around the wound. As the groove grew deeper, the healer scraped more slowly: he wanted to avoid breaking through the skull too violently and cutting into the brain. Eventually, the knife broke through the cranium and he carefully lifted out the fragments, leaving an almost perfectly round hole. Job done, the healer covered the wound with a poultice of herbs and left. After the day's skirmish, he had several other patients waiting.
Ever since the first neatly perforated prehistoric skull came to light in the 1860s people have argued about what the holes were for. Did they do it for mind-altering reasons like Feilding? Or is the picture of the Peruvian healer nearer the mark? Perhaps it was some ancient religious ritual to which priests submitted, believing that it would bring them closer to the spirit world. Or maybe it was performed to appease the gods—the victim held down during the operation. One of the most popular ideas is that the holes were made to let out the demons thought responsible for illnesses such as epilepsy. A few dissenters, though, have always argued that trepanation could have been performed for sound medical reasons, to treat fractured skulls, blood clots or abscesses under the skull.
Magic or medicine?
"There was debate from the start," says John Verano, a biological anthropologist at Tulane University in New Orleans. "Was it done for medical reasons or was it something primitive, done for illogical reasons?" The idea of magic and demons fitted many people's concept of primitive savages rather better than the notion of prehistoric people skilfully operating so close to that most vulnerable of human organs, the brain. But hard evidence to answer the question once and for all has been frustratingly elusive. Skulls with holes in them have been unearthed all around the world, from northern Europe and Siberia to the Mediterranean and the Americas, but most investigators have studied only a few specimens. What's more, the holes are not always the result of trepanning (see "What's in a hole?").
After 10 years of detective work among museums and private collections in the US and Peru, Verano believes he has seen enough skulls to answer the question with certainty. Trepanation was a lifesaving operation. "There is no convincing evidence for the religious stuff," he says. But there is plenty of evidence for advanced surgical skills among the prehistoric people of the Andes. Trepanation was emergency surgery to remove shattered bits of bone from fractured skulls and clean out the blood that often pools under the skull after a blow to the head. Scattered evidence from other parts of the world suggests people everywhere were trepanning for the same reason, says Verano.
The Andean region from the northern border of Peru south into Bolivia has produced more trepanned skulls than the rest of the world together—around a thousand so far. Verano has studied 650 of them, enough to show a clear link between head wounds and surgery. And with skulls spanning two thousand years, from around 400 BC to AD 1500, he can match improvements in surgical techniques with a remarkable increase in the survival of patients to a level that rivals that under today's surgeons.
The earliest trepanners of the central Andes were the people of Paracas on the south coast of Peru. Around 400 BC their surgeons were performing a relatively crude type of operation, scraping away the bone around a head wound with obsidian tools. They tended to remove large, irregular-shaped pieces of skull. In the process, they often removed all sign of the original fracture although Verano has found some telltale cracks. "This was radical surgery. They were making large holes. But there are examples of skulls with extensive healing, which means the patient survived." In fact, around 40 per cent of the patients lived through the operation. The signs of survival are clearly written in the bone of the skull. If the patient dies, the edge of the hole remains rough, showing the marks of the surgeon's instruments. If the patient lives, the bone around the wound begins to change immediately. The rough bone is resorbed, eventually producing a smooth rim around the hole. The extent of the smoothing gives some indication of how long the patient lived after the operation.
The largest number of trepanned skulls—457—come from the central highlands of Peru, and date from AD 900 to around AD 1500. These people were quite different from those of Paracas, separated by high mountains and many centuries. But their surgeons carried out the same operation and for the same reasons. They had a wider repertoire of techniques for removing bone, and sometimes tried several of them on one skull. As well as the scraping seen on the Paracas skulls, surgeons occasionally made deep, straight cuts to remove a square of bone, leaving criss-cross cut marks like a noughts and crosses grid. They also adopted a technique that looked like the work of a pastry cutter—boring a ring of holes and then cutting the bridges of bone between them. "They seemed to be experimenting with different techniques," says Verano. "And some of them were more successful than others."
The skulls of the central highlanders provide the clearest evidence that trepanation was a treatment for fractured skulls. More than 30 per cent of the trepanned skulls still bear the signs of the original fracture. "This suggests the technique was developed because there were so many head injuries," says Verano. "We find lots of dents in heads—both in people who were trepanned and those who weren't." More than half the men in the region had at least one skull fracture—but so did 32 per cent of the women and 27 per cent of the children. In formal warfare, most of the injured would be men, so the fact that men, women and children all had cracked skulls suggests that they were attacked during raids on their villages. "This was a real rough neighbourhood," says Verano.
The local weapons were slingshots and war clubs. Both inflicted terrible injuries. Verano has seen the signatures of those weapons on skulls. "They punched right through or smashed the bone," he says. Graham Martin, a neurosurgeon at Wellington Hospital in New Zealand, calculates that a stone from a slingshot would hit the skull with the same force as a bullet fired from an 18th-century pistol. "It can inflict a considerable fracture from a distance of 50 or 100 metres," he says. No wonder the local healers were experimenting with trepanation.
The most successful surgeons were the Incas, who started out in the southern highlands of Peru around Cuzco but went on to conquer most of the central Andes before the Spanish arrived and put an end to their empire in 1532. The Incas' ancestors began trepanning around AD 900, but the operation became almost an art form under the Incas themselves, around AD 1350 to 1400. The Inca surgeons used all the techniques seen elsewhere but preferred a fourth method—circular grooving, gouging out a bevelled ring of bone with a sharp instrument. "In some cases the surgeons' skills were very impressive. They made nice round holes and there was good long-term healing. The Incas were doing better surgery than many later surgeons in Europe," says Verano. The Incas had a success rate of around 80 per cent. In Europe and America in the 19th century and early 20th century, surgeons operating on the skull were lucky to save 25 per cent of patients.
How did the Incas and their neighbours achieve such remarkable success? They probably learned very quickly to avoid cutting through the dura mater—the brain's tough outer membrane—or damaging the blood vessels in the brain. "It would have been obvious very quickly that patients cut this way died and those with an intact membrane around the brain survived," says Verano. After that, the key to success was to avoid infecting the wound. And in prehistoric Peru, patients were less likely to pick up an infection than in 19th-century London or Paris. The ancient surgeons didn't have hospitals, which were hotbeds of infection in the days before antibiotics. Prehistoric surgeons also used stone tools, which cut through bone remarkably quickly, and they probably used a new one each time they operated—unlike later surgeons with expensive but unsterilised steel instruments. Healers would have been well versed in herbal medicine and known about plants with antibiotic properties. "They knew how to sterilise and clean wounds," says Verano.
Over the centuries, the surgeons of Peru made ever smaller holes and their success rate improved. Scraping and circular grooving had the best survival rates. The surgeon had more control and could carve away the bone with more precision, reducing the risk of damaging the brain. Straight cutting or drilling was riskier: the chances of suddenly breaking through the skull and penetrating the brain were higher—and this almost invariably spelt death for the patient. Verano suspects that surgeons may sometimes have had to trade safety for speed. "If the patient had multiple head injuries then perhaps straight cutting was faster. Like a surgeon today the healer would rush to get the head open quickly if he needed to stop bleeding. But if there was time, he could have used a safer technique like scraping."
The success rate and the choice of a particular technique suggest that there really was such a thing as a surgeon, a healer who was skilled in trepanation. In regions where they got a lot of practice, they might even have begun to learn something about the way the brain works. "I would expect in ancient Peru people may have learned early on that some changes in behaviour were linked to brain damage," says Verano. "People hit on the left side of the head, for instance, might be paralysed on the right or they might lose the power of speech. They could have linked these conditions to particular regions of the brain. I bet in cultures with a high incidence of head injuries people learned a lot about the effects of those injuries."
It is possible that as healers learned more about the head and brain and realised they could cut holes in the skull relatively safely, they might have experimented with trepanation as a treatment to relieve other neurological symptoms—persistent headaches or dizzy spells, perhaps even removing brain tumours. Once patients realised how good the surgeons were, they might even have elected to have surgery. "We can only speculate here," says Verano. "Unless there is some mark left on the bone to indicate what was wrong you can't ever know."
However, attempts to treat persistent symptoms might help to explain one unsolved mystery: why do some skulls have several holes, made at different times? It's highly unlikely that they were all made to treat fractures. They might be repeat treatments to get rid of pains that lingered long after the original operation. There is one Inca skull from Cuzco with seven large, trim holes and signs of healing around each of them. "I think this one was a hypochondriac," says Verano. "He kept coming back for more saying 'I still have a headache . . . '"
What's in a hole?
TREPANATION has always fascinated people. The mix of magic and medicine is a potent one. And that, says Bob Arnott, an archaeologist at the University of Birmingham, has made people all too quick to say any hole in the head indicates trepanation. Some holes, however, were made after death, as part of a burial rite, or to allow removal of the brain before mummification. In some societies, people wore bone amulets—little discs cut from the skull of a leader or great warrior. "If you wore a bit of a great man around your neck some of his greatness might rub off. It was a bit like ripping the clothes off a pop star in the 1960s," says Arnott.
In some parts of the world, warriors displayed the skulls of defeated enemies as trophies, stuck on the end of a pointed stick or hung from a string fixed through a hole in the cranium. And sometimes, the holes weren't even made by humans, but animals gnawing at the dead. And there's always the possibility that the holes were made by budding surgeons honing their skills on the dead, suggests Charlotte Roberts, a palaeopathologist at the University of Durham.
Some people live quite happily with perforated skulls that are nothing to do with surgery. In most people the bones of the skull close during early childhood, but in some the gaps remain. These can be as large as a coin and perfectly round. Disease can also carve holes in the bones of the skull. Syphilis and brain tumours both leave defects in the skull. And among older people, the parietal bones at the side of the head can thin progressively until they have a neat pair of holes.
Of course, there are holes made by weapons that healed without a surgeon's help. Blows from an axe or a sword usually leave distinctive straight slashing cuts, but picks and slingshots can punch a hole as neat and round as anything made by a surgeon.