Skeleton 150 May Be the First Known Trebuchet Trauma Victim

Around seven centuries ago, a man in Scotland experienced an exceptionally terrible day.

He was simply getting on with life when something suddenly intervened.

It struck him from behind with such immense force that it broke his skeleton in more than 160 separate places.

Researchers now believe they have identified the object that hit him: a projectile launched by a medieval siege engine.

Their leading suspect is a trebuchet, a powerful weapon that used a descending counterweight to throw heavy missiles at enemy defences.

Should that conclusion prove correct, the remains of the young man, called Skeleton 150, would provide the first known archaeological evidence of trauma caused by a trebuchet.

"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."

Skeleton 150 and the sieges of Stirling Castle

Stirling Castle stands on a tall crag above Stirling, commanding views over the River Forth. The location was selected for its excellent visibility and the difficulty of attacking it. Occupied from at least the early 12th century, it served as the seat of successive generations of Scottish monarchs.

In the late 13th and early 14th centuries, the castle became strategically vital and an important symbol during the Wars of Scottish Independence between Scotland and England. It was a valuable prize that the English sought to capture and the Scots, unsurprisingly, sought to retain.

The fighting for the castle was brutal and bloody, with control passing back and forth repeatedly as the wars continued. Skeleton 150 was among several people whose remains are linked to this violent era.

"The injuries are comparable to people hit by trains and cars today." - bioarchaeologist Dr Jo Buckberry

Analysis of his bones indicated that he was approximately 22 to 34 years old at death. Radiocarbon dating, calibrated by Dr Cathy Batt at the University of Bradford, dates his death to between 1255 and 1405 CE, a period during which the castle endured repeated sieges.

Yet even among people whose remains show violent deaths, Skeleton 150 stood out.

"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."

Reconstructing the high-energy injuries

This reconstruction required careful, painstaking work. Although the skeleton was nearly complete, many of its bones had been severely fragmented.

The team methodically reassembled as many pieces as they could, using radiography, microscopy and micro-CT scans to support their assessment.

The result was a pattern of damage not previously identified in medieval human remains.

Evidence of medieval warfare on skeletons is usually defined by weapon marks: blade cuts, wounds from thrusting weapons and projectile injuries. In contrast, Skeleton 150 had suffered an exceptional level of blunt-force trauma.

Some of his fractures showed that this was not ordinary blunt-force damage.

"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 difference matters, because a large, heavy item will not necessarily cause identical injuries merely because it has substantial mass.

One possible explanation considered by the researchers was falling masonry.

"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 gauge the scale of the forces involved, the researchers drew on modern forensic medicine, using methods unavailable only a few decades ago.

Computed tomography has enabled forensic experts to conduct “virtual autopsies”, or virtopsies, which create detailed 3D records of injuries with known causes, including falls, gunshot wounds and vehicle crashes.

Buckberry and Randolph-Quinney essentially reversed that process. They rebuilt Skeleton 150’s fractures in three dimensions and compared their pattern and anatomical relationships against injuries recorded 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.

As Buckberry put it: "The injuries are comparable to people hit by trains and cars today."

Why a trebuchet is the likely weapon

However, the fracture pattern showed considerably more than the sheer force of the impact.

Using their expertise, the researchers examined the fracture directions and patterns to establish the man’s position when the projectile hit him.

Bones initially fracture under tension on the side opposite the applied force. A particularly informative fracture appeared 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.

This evidence indicates that his arms were bent in front of him, somewhat like a praying mantis, when he was struck. Fractures in his lower body further indicate that he was standing upright, supporting his weight on his legs and feet, with his back facing the projectile.

The object that hit him was clearly substantial. Damage ran from his head to the middle of his back and affected both shoulders, every rib and numerous vertebrae.

Buckberry said the scale of the injuries points to a "substantially large projectile", though the researchers cannot currently calculate its dimensions, mass or speed.

"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.

What, then, could have launched a large, heavy object with enough speed in medieval Scotland to produce injuries resembling those of 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.

There were four potential sieges during the period established by radiocarbon dating: 1299, 1304, 1314 and 1337.

The 1304 siege is especially intriguing, as it was the battle in which King Edward I of England used his celebrated War Wolf trebuchet against Stirling Castle.

Nevertheless, Edward I possessed several siege engines during that confrontation, which lasted for months. Nor is there currently any means of establishing whether Skeleton 150 died in 1304, much less whether War Wolf killed him.

Regardless of who caused Skeleton 150’s death, his remains could offer a rare view of a type of medieval violence otherwise absent from the archaeological record.

Why, then, are trebuchet victims so uncommon? By the 13th century, counterweight trebuchets were widely used in Europe and had become a central feature 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 disappeared from the archaeological record. Their skeletons would need to have survived centuries of reconstruction, then been excavated and preserved, before finally being assessed by somebody able to tell this particular blunt-force trauma apart from damage sustained 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, supported by Historic Environment Scotland, was presented in August at the 25th European Meeting of the Paleopathology Association.

This article was fact-checked by Rachel Garner and edited by Peter Dockrill. Although we take pride in our process, we are only human. If you notice an error, please tell us.