Some seven centuries ago, a man in Scotland had a terrible, horrible, no-good, very bad day indeed.
There he was, going about the business of living, when something interrupted.
Something that slammed into him from behind with such tremendous force that it shattered his skeleton in more than 160 places.
Now, scientists think they know what hit him: a projectile hurled by a medieval siege engine.
The most likely culprit? A trebuchet – a formidable weapon that used a falling counterweight to hurl heavy projectiles at enemy fortifications.
If they're right, the young man's remains, known as Skeleton 150, represent the first known evidence of trebuchet trauma in the archaeological record.
"His death would, fortunately, have been essentially instantaneous," bioarchaeologist Dr Jo Buckberry of the University of Bradford in the UK told ScienceAlert.
"The worst fractures are to the back of the head on the right side, and the right shoulder, and these came from behind. While the left shoulder is also impacted, it is less fragmented, suggesting a slightly lower force there."
Stirling Castle sits atop a high crag in Stirling, overlooking the River Forth – a site strategically chosen for maximum visibility and minimum pregnability. It's been around since at least the early 12th century, the seat of many generations of Scottish monarchs.
During the late 13th and early 14th centuries, it became both strategically important and a potent symbol in the Wars of Scottish Independence between Scotland and England – a rich prize the English wanted to take and the Scottish, understandably, wanted to keep.
The battles over the castle were fierce and bloody, and it changed hands repeatedly as the wars dragged on. Skeleton 150 was one of several individuals whose remains are associated with this violent period of history.
"The injuries are comparable to people hit by trains and cars today." - bioarchaeologist Dr Jo Buckberry
Examination of his remains revealed that he was between about 22 and 34 years old when he died. Radiocarbon dating, calibrated by Dr Cathy Batt of the University of Bradford, places his death sometime between 1255 and 1405 CE – a window in which the castle was besieged repeatedly.
But even among the remains of people who died violently, there was something extraordinary about Skeleton 150.
"As someone used to seeing trauma in modern casework situations, what really surprised me was the fact that this looked so much like a forensic case," forensic anthropologist Dr Patrick Randolph-Quinney of Uppsala University in Sweden told ScienceAlert.
"The sheer magnitude of trauma massively disrupted the body and caused 160-plus fractures, but we were still able to reconstruct the biomechanical narrative of this trauma after seven centuries."
That reconstruction was delicate and painstaking. Although the skeleton was almost complete, many of his bones were highly fragmented.
The researchers carefully pieced together as many fragments as possible, supplementing their examination with radiography, microscopy, and micro-CT scanning.
What emerged was a damage pattern unlike anything previously recognized in medieval remains.
Skeletal evidence of medieval warfare is dominated by the marks left by weapons – cuts from blades, wounds from thrusting weapons, and injuries inflicted by projectiles. Skeleton 150, by contrast, had been subjected to an extraordinary amount of blunt-force trauma.
And not just any blunt-force trauma, as some of his fractures revealed.
"The exact reason why bone undergoing failure produces these zigzag patterns is poorly understood," Randolph-Quinney said.
"But – even though the underlying mechanism is not fully understood, we can say with certainty that this zigzag pattern is only produced when very high energies transfer to bone. You don't see it at lower energy levels, so this is a kind of smoking gun for high-energy failure."
That distinction is important. A large, heavy object doesn't necessarily produce the same injuries simply because it carries a lot of weight.
Falling masonry, for instance, was one alternative explanation the researchers considered.
"The deep zig-zag nature of the fractures indicates a very high-velocity impact," Buckberry said. "Falling masonry would have lower velocity, and it is unlikely they would look the same."
To understand the magnitude of the forces involved, the researchers turned to modern forensic medicine – tools that wouldn't have been available just a few short decades ago.
Computed tomography has allowed forensic scientists to perform "virtual autopsies", or virtopsies, producing detailed 3D records of injuries from known causes of death – including falls, gunshot wounds, and vehicle collisions.
Buckberry and Randolph-Quinney effectively worked backward. They reconstructed Skeleton 150's fractures in three dimensions, then compared their pattern and anatomical relationships with injuries documented in modern forensic cases.
"The only match for both the fine detail and the massive magnitude of trauma is high-energy forensic cases such as uninterrupted falls from great height and vehicular accidents," Randolph-Quinney said.
Or, as Buckberry noted: "The injuries are comparable to people hit by trains and cars today."
The fracture pattern, however, revealed far more than just the brute force involved.
In a magnificent display of sheer skill, the researchers used the pattern and direction of the fractures to determine the man's posture when the projectile struck.
Bone first begins to fracture under tension on the side opposite the force acting upon it. One particularly revealing break was found in one of Skeleton 150's arms.
"There is clear evidence of the point of tension in a fracture to the right ulna, where the point of tension is on the anatomical posterior of the bone," Buckberry explained.
Based on this evidence, his arms were bent in front of his body, a little like a praying mantis, when he was struck. The fractures in his lower body also suggest he was upright, bearing his weight through his legs and feet, with his back to the projectile.
Whatever struck him was hefty. The damage extended from his head to his mid-back, across both shoulders, all of his ribs, and many of his vertebrae.
Buckberry said the extent of the injuries suggests a "substantially large projectile", although the researchers can't yet estimate its size, mass, or velocity.
"We cannot say for certain that all of these injuries were from the impact itself (rather than resulting from the transfer of energy), but they are consistent with a single large object moving very fast," she said.
So, what in medieval Scotland could propel a large, heavy object fast enough to inflict injuries comparable to a modern vehicle collision?
"As far as we know, there was only one mechanism capable of moving a heavy mass very fast during the medieval period – a siege engine such as a trebuchet – hence our conclusion," Randolph-Quinney said.
And when did this very bad day occur? There were four possible sieges within the timeframe specified by the radiocarbon dating – 1299, 1304, 1314, and 1337.
The siege of 1304 presents a particularly tantalizing prospect – the battle in which King Edward I of England deployed his famous War Wolf trebuchet against Stirling Castle.
But Edward I had a number of siege engines at his disposal during that months-long stand-off; and besides, there is currently no way to know whether Skeleton 150 even died then, let alone whether War Wolf killed him.
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Whoever killed Skeleton 150, his remains may offer a rare glimpse of a form of medieval violence that has otherwise vanished from the archaeological record.
But why are trebuchet victims so rare? By the 13th century, counterweight trebuchets were in general use in Europe, becoming a mainstay of medieval siege warfare.
"We don't know how many people were killed by trebuchets, and it's probably not that many. These weapons were developed to force a surrender and breach walls, rather than kill individuals," Buckberry explained.
Other victims may simply have been lost to the archaeological record. Their skeletons would have needed to survive centuries of rebuilding, be excavated and retained, and ultimately be examined by someone able to distinguish this kind of blunt-force trauma from damage that occurred after death.
"It's likely that any bioarchaeologist working today would recognize the trauma, but this was not the case 20 or 30 years ago," Buckberry said.
The research, funded by Historic Environment Scotland, was presented at the 25th European Meeting of the Paleopathology Association in August.
This article was fact-checked by Rachel Garner and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.