Archaeologists have uncovered early evidence of brain surgery after the discovery of two brothers buried beneath the floor of a late Late Bronze Age-era building.
The young men were buried between 1450 and 1550 BC in what is now the urban centre of Megiddo, Israel.
Their remains were discovered in 2016, but it wasn't until a year later that archaeologists made an exciting discovery: one brother's skull showed evidence of cranial trephination.
Basically, he'd had surgery on his head to remove a square piece of skull from his frontal bone.
Rachel Kalisher, a PhD student at Brown University in the US and lead author of the study published in PLOS ONE, initially thought the skull fragment had been taken as a DNA sample by colleagues.
Realising the fragment had been removed in antiquity was a "crazy moment", she said.
"Usually when you study human remains, you're studying the accumulated change that they experienced throughout their lives, but this was one moment captured."
What is a cranial trephination?
Trephinations are surgical procedures where a hole is created in the skull by removing a piece of bone, all without affecting the underlying tissue.
They're most often cited in archaeological literature as a way to cure head trauma by releasing pressure in the head.
The procedure may have been performed on people with conditions such as epilepsy, scurvy, sinusitis and intracranial disorders.
Ms Kalisher believes this person was alive when the trephination was carried out.
"It still seemed to be what we call 'green bone', so it was still living at the time, and we can tell this based on the colouration of the bone, the smoothness and shininess of the bone, and also that the inner table of bone itself was preserved," she said.
"With this [cut to the skull] not going all the way through and hurting the underlying soft tissues, there was some kind of caution exercised."
Earliest evidence of this particular style
In the Levant region, which spans modern Jordan, Israel, Palestine, Syria and Lebanon, there are only a few dozen examples of trephination in the archaeological record.
While this latest discovery is not the first example of trephination — even for this area — it is the earliest evidence of this particular style by at least several centuries.
Earlier methods involved drilling with a round instrument or scraping, but Ms Kalisher said the trephination carried out on the Megiddo brother was unique.
The cuts were precise, left smooth edges, and were made at around 90 to 100 degrees.
"This trephination is called an 'angular notch definition', and what that means is essentially these intersecting hashes would be drawn and then pieces will be wedged out piece by piece," Ms Kalisher said.
"The precision of this surgical procedure, at least to me, seems like something that would have been done by a professional, especially if you're talking about an elite individual with the means to get that experience."
Griffith University archaeologist Tim Maloney, who was not involved with the study, called the findings "fascinating and horrific".
"The human cranium is an incredibly robust part of the skeleton. At minimum, it must have taken hours to create those notches.
"Although it seems rather crude and 80s-horror-movie-looking, it was, at the same time, quite precise and conducted by surgeons that had a good understanding to not penetrate the soft tissue layers beneath the bone.
"Most typically in this sort of Bronze-Age era ... [trephination was] typically used as a proactive treatment for acute trauma, battle trauma and injuries of the like."
What do we know about the brothers?
They died within one to three years of each other, but were buried together under the floor of a house, a common practice for the area, Ms Kalisher said.
The brother who underwent trephination died soon after the procedure and was aged between 21 and 46 years old.
Ms Kalisher said considering there was no healing to the skull, he could have died within minutes, days or weeks of the surgery.
"We're talking a really short period of time ... he did not survive very long," she said.
The trephination could have been the reason the brother died, but he may already have been fatally ill.
As for the other brother, he died aged in his late teens to early 20s.
Both brothers' remains exhibited evidence of bone remodelling consistent with chronic infectious disease.
The brother who had the trephination had extensive bone lesions, a sign of some kind of infection.
"It could be that this trephination was some kind of intervention to a declining state of health, but because I don't know exactly what the disease was, I can't say for certain," Ms Kalisher said.
Dr Maloney said the DNA preservation of the brothers makes the case "remarkable".
"DNA preservation confirmed that they were brothers, they lived in the same socio-economic [setting] and probably in the same domestic setting, sharing similar genetic traits but also genetic predisposition to these diseases.
"Those biological circumstances combined with a pretty clear social status is unique to archaeology."
He added the excavation provided "an absolute smorgasbord of horrific health conditions" in both skeletons.
"What I think is most remarkable from this, and all other early cases for medical interventions in our shared human story, is that it's a strong case for a caring society," he said.
"It might sound simple to think of people caring for their family, their brothers, their children, their community, but there's rarely direct archaeological evidence for that social community care."
