A Neanderthal who died 75,000 years ago may have been struck through the chest by a sharpened wooden spear, archaeologists say.
They say a 15mm hole found in a shoulder blade in a cave in Iraqi Kurdistan could be the earliest evidence of lethal violence involving such a weapon.
From the angle of the wound and other evidence, the researchers believe the spear entered the individual's chest and passed through the body - probably damaging a lung and major blood vessels - and exited through the left shoulder blade to leave a near-perfect hole.
The research is the latest in emerging evidence that suggests Neanderthal societies experienced more violence than previously thought.
Neanderthals were a separate species of humans that went extinct around 40,000 years ago. They lived across a large expanse of Europe and western and central Asia, and sometimes overlapped with our species, Homo sapiens.
The wounded Neanderthal's remains were found in a cave in Iraqi Kurdistan. As well as the left shoulder blade, the individual's right hand, three ribs and some teeth were also found.
A hole in the shoulder blade may be the earliest evidence of "lethal interpersonal violence" from a wooden spear, according to Dr Emma Pomeroy, study lead author from Cambridge's Department of Archaeology.
"The fatal strike may have been an intended heart shot," she told BBC News.
Archaeologists call the remains Shanidar A, named after the cave in which they were found. Remains of at least 10 Neanderthals were discovered in excavations in the cave in the 1950s.
The wound is thought to be the first evidence for use of sharpened wooden spears in the prehistoric Middle East, according to Pomeroy.
"It is not the kind of break that you would get naturally, because it is so circular," she said. "Experiments with reconstructed wooden spears produce very similar round holes in bone."
But the interpersonal violence is by no means certain, she says. It may be a case of friendly fire, a wound caused as a result of a hunting accident.
But Prof Chris Stringer of the Natural History Museum in London, who was not involved in the research, told BBC News that an attack by a rival was the more plausible explanation.
"The researchers leave it open whether this resulted from a hunting accident or interpersonal violence, but in my view the latter seems more likely, given the positioning and extent of the wound," he said.
This discovery has echoes of an earlier find in the same cave, in 1957. Those remains involved another Neanderthal who lived more recently, around 50, 000 years ago. Their ribs had evidence of a partly healed wound, which archaeologists believe was probably caused by a stone-tipped spear.
We can't tell for sure whether these Neanderthals were hurt by a companion during a hunt or murdered by a rival. But they join a small but growing body of evidence which point to the possibility that human-on-human violence was more common and goes back further than the current scientific consensus would suggest.
"I unfortunately see the growing body of evidence as an indication that interpersonal violence goes deep into human prehistory," Stringer told BBC News.
A key piece of that evidence is a study published in 2022 of very early Neanderthal skulls from northern Spain at an archaeological site called "the Pit of Bones". It suggests that deadly violence was taking place about 430,000 years ago.
Researchers found 57 healed head injuries among 20 individuals. Nine individuals had potentially fatal skull fractures. Six had similar puncture wounds at the back-left of the head. Because the wounds repeatedly occurred in almost the same place, the researchers concluded that deliberate blows were more likely than accidental damage. One skull had two wounds that had probably been inflicted with the same object.
The Pit of Bones findings do not show that everyone in this population was habitually violent, but they provide strong evidence that repeated killing occurred among these people hundreds of thousands of years ago.
For decades, many archaeologists linked the beginnings of organised warfare to farming, when people began living in permanent settlements and competing over land, livestock and food stores.
But evidence from earlier hunter-gatherers and still older human relatives has since shown that individual killings pre-date farming by a very long way.
The live scientific debate is over how common such violence was, and when sporadic attacks became organised conflict and wars between groups.
The research has been published in the journal Scientific Reports.