The 10,000-year-old bones bear the blunt marks of a violent death.
The skeleton of one man lay with half his skull and torso sunk into the ground. He had been hit in the front of the head, and stabbed in the neck with a pointed weapon. Another, the skeleton of a woman in the late stages of pregnancy, was found face-up with her knees bent toward her. Like a few others, her hands were clumped together as if they had been bound.
There are 12 complete skeletons in all, along with the partial remains of 15 additional people, unearthed near what was once a lagoon by Lake Turkana in northern Kenya.
The prehistoric massacre is the first sign of intergroup violence to have been discovered in a nomadic hunter-gatherer society, according to researchers from Cambridge University and the Turkana Basin Institute who published their findings in the journal Nature Wednesday.
Notably, the trauma sustained by at least 10 of the skeletons may indicate that human warfare dates back to far earlier than has been believed.
"If you take war to mean lethal conflict between groups, the idea is that war in that sense only arose when people had food production, when they had livestock and agriculture — things that could be stolen," one of the study's co-authors, Robert Foley, said in a phone interview with The Washington Post early Thursday. "This suggests perhaps that intergroup conflict may extend much deeper into our evolutionary past."
The origins of war are a subject that has been hotly contested in the scientific community, as it is unclear whether humans are naturally predisposed to conflict between groups, or if warfare emerged only after settler societies created the conditions for raiding resources.
Scientists found the skeletons at the Kenyan site Nataruk as part of a years-long project led by Cambridge scientist Marta Mirazon Lahr. She began investigating the bones in 2012, when an assistant noticed the curved back of a skull jutting out from the sediment.
According to Foley, the skeletons appear to have belonged to a group of hunter-gatherers living at the time on the lush, marshy edge of a lagoon where they used bone harpoons to fish and hunt. They were likely more sedentary than most foraging communities, as there are indications that the environment was quite rich.
Although any guesses as to why they were killed are speculative, Foley said it is possible that another group found the area attractive and competed for it.
Whereas most groups of skeletons are found on the site of ancient cemeteries, the scientists believe that these were never given a deliberate burial.
"They're in all sorts of positions," Foley said. "They are lying where they died."
The other strong evidence for violent encounters between bands of nomadic hunter-gatherers comes from a graveyard in Jebel Sahaba, Sudan, where 23 bodies out of 58 show signs of having met violent ends. But these were buried in a cemetery, which indicates a degree of settlement closer to later civilizations than the Nataruk hunter-gatherers.
Still, it is possible that the Nataruk massacre was also similar in many ways to the raids that would overtake later territorial communities. In the same area around Lake Turkana, some remnants of blades and evidence of pottery hint that while the band of people lived a nomadic lifestyle, they may have owned things of value that warranted brutal thievery.
Hence the debate about how long humans have been at war rages on, with some scientists expressing skepticism that this particular conflict qualifies.
"Based on skeletal evidence from one site in an area, it may be jumping the gun to call this 'war,' " Douglas Fry, an anthropology professor at the University of Alabama told the New York Times, adding that war should involve "fortifications, villages built in defensible locations, specialized weapons of war, artistic or symbol depictions of war. ..."
What isn't under dispute is the devastation that the community suffered. The remains include that of six children — one teenager and others under 6 years old — as well as a fetus with a gestational age of 6-9 months.
"At the end," Mirazon Lahr told Reuters, "all massacres are savage."