Between 2,300 and 2,500 years ago, up in the Altai Mountains of Siberia, a man sustained a serious head injury. It's believed that head injury left him with a blood clot between his brain and his skull. Afterwards, likely, he would have had intense headaches and movement problems. He would have vomited, more than a person should. And so, perhaps in an effort to cure him, without any of the knowledge or tools available to modern neurosurgeons, a large hole was chiseled into his skull.

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Despite that, with a lasting hole in his head, the man survived.

We know this because his skull, discovered in Siberia last year, shows signs of healing over the broken bones. It was found and analyzed along with two other skulls from the same era that also show signs of trepanation, the oldest known form of neurosurgery. Now, as reported by the Siberian Times, a team of neurosurgeons, anthropologists and archeologists say that—thanks to a series of hands-on experiments—they have a clearer image of just how such early medical feats were accomplished.

The team from the Russian Academy of Science' s Institute of Archaeology and Ethnography first studied each skull under a microscope to deduce the instrument likely used to detach pieces of bone. They ultimately concluded that a single kind of tool—a bronze knife—was employed to make the holes in two stages, explains the Siberian Times, quoting neurosurgeon Aleksei Krivoshapkin:

First, a sharp cutting tool removed the surface layer of bone carefully without perforating the skull itself. Then, with short and frequent movements a hole was cut into the skull. Professor Krivoshapkin said: 'All three trepanations were performed by scraping. From the traces on the surface of the studied skulls, you can see the sequence of actions of the surgeons during the operations. 'It is clearly seen that the ancient surgeons were very exact and confident in their moves, with no traces of unintentionally chips, which are quite natural when cutting bone.'

An archeologist made a replica of the kind of knife likely used. Next, Krivoshapkin attempted to replicate the 2,300-year-old surgery using a modern-day skull (no longer attached to a person, of course). According to The Siberian Times, it took him 28 minutes and some considerable elbow grease to accomplish the task, but the results “were found to mirror those found in the ancient patients.”

The team notes that the people of the Pazyryk tribe, to which the Altai Mountain skulls belonged, were skilled in working with animal bones to make different tools and objects. That knowledge likely aided them in their surgical attempts on humans, though archeologists involved think the culture may have also been aided by some of the medical teachings coming from ancient Greece.

While scientists now better understand the techniques of early trepanation in Siberia, there’s one question left unanswered: did the ancient patients have any kind of anesthesia to help them through the no doubt agonizing experience of having their heads cut open? We can hope they did, but bone samples don’t offer conclusive insight into such mysteries.