Incan doctors scraped holes in skulls with stone tools — and the patients survived
Skull surgery performed with stone tools during Inca Empire times remarkably successful
Skull surgery during the time of the Inca in Peru was performed with amazing skill and success, considering the primitive tools available.
The surgery, known as trepanation, involves drilling, cutting or scraping a hole in the skull, and has been practised by many civilizations throughout history. The first known case is from Europe 5,000 years ago. In the New World, it dates back about 2,500 years.
Anne Titelbaum, a bioarchaeologist at the University of Arizona, and her colleagues focused their study on ancient Peru, studying a trove of trepanned skulls ranging from the earliest evidence in the Americas to up to the 15th century, the time of the Inca Empire.
The skulls revealed some of the reasons ancient Peruvians may have suffered this kind of skull surgery, according to Titelbaum.
"Cranial trauma could have occurred from blunt force trauma through the use of weaponry like sling stones, clubs and maces. So in many cases it seems that the surgery was done to treat head injuries: perhaps to clean up the wounds, maybe remove pieces of broken bone and alleviate hematomas and associated intracranial pressure."
She points out that not all the skulls show signs of this kind of injury. Evidence from history suggests that trepanation was also done for treatments of other ailments from headaches to epilepsy, and possibly had ritual purposes as well.
Scraping into the skull with stone tools
In ancient Peru, the holes in the skull were most likely made using sharpened stone tools. Given the primitive conditions for performing surgery of any description, death was a distinct possibility. But one of the three known methods of making the cuts was less risky than the others.
"There were various techniques that were used in prehistoric Peru including cutting, drilling and scraping," says Titelbaum. Each had drawbacks. Linear cutting, with a sharp stone knife, often required cutting larger areas than necessary. Drilling also risked taking out more material than was desirable. And both techniques ran the risk of going too deep.
"Scraping was probably the technique that yielded the best success rates, and that's likely because the bone could gradually be removed with more control and that would prevent a surgeon from penetrating too deep."
The problem with cutting too deep is that the surgeon would risk piercing the membrane that sits beneath the bone called the dura mater. The dura mater surrounds and protects the brain and also helps keep out infection. By studying the edge of the bone at the cut marks, scientists estimate whether the healing process was long or short-term — in other words, whether the patient lived and for how long.
The earliest group of skulls — those from nearly 2,500 years ago — showed that only 40 per cent of people survived. Another group from almost 1,000 years ago indicated a 53 per cent survival rate. Inca surgeons 500 years ago had dramatically improved that survival rate to about 80 per cent.
"Over time, from 2,500 years ago all the way up to the 15th century, there's definitely evidence of improvement, and that is shown in the size of the trepanation, the skill of the trepanations, the techniques of the trepanations and by the overall success rate of the patients," Titelbaum says.
"Trepanation and the success of these surgeries speaks volumes about the ingenuity and the skills of the prehistoric people in Peru and it culminates with the Inca," Titelbaum says. "The Inca were incredible architects and engineers and it's no surprise that they should also have a very sophisticated form of surgery."