A pregnant woman with her hands and feet bound. A man with an obsidian blade embedded in his skull. Men and women with arrow wounds to the head and neck.

That's the grisly scene archaeologists describe at Nataruk, in modern-day Kenya, where they say they've uncovered unique evidence of violence in prehistoric, nomadic hunter-gatherer communities.

The massacre they've uncovered is striking, they say, because it pushes back against a theory that warfare didn't become a feature of human culture until communities settled down.

Archaeologists from Cambridge University excavated the remains of 27 people, including at least eight women and six children, in a region that was once the edge of a lagoon, near modern-day Lake Turkana. The remains included 12 skeletons that were fairly complete, "preserved by the particular conditions of the lagoon," the researchers write in Nature this week.

They all appeared to have died at the same time, 10,000 years ago or so. The researchers focused on the 12 skeletons — 10 showed evidence of fatal injuries, including sharp-force and blunt-force trauma, and several had blades or projectiles embedded in them.

Two of the skeletons — including a woman who either was in the late stages of pregnancy or was holding a newborn baby — showed no evidence of trauma, but their hands were in a position suggesting they might have been bound.

The bodies did not appear to have been carefully or ritually buried.

The site of the massacre suggests something more than an interpersonal conflict, the researchers say. There's plenty of evidence for violence between nomadic individuals, but prehistoric violence between two or more large groups is harder to identify.

As a result, "the origins of war are controversial," the researchers write. Were humans waging war as nomadic hunter-gatherers, or did communities only engage in warfare once they'd established agriculture and permanent settlements?

The oldest known evidence of warfare — the Jebel Sahaba graveyard, in modern-day northern Sudan — is estimated to date to around 13,000 years ago. It contains the remains of bodies killed in violent skirmishes, but the use of the cemetery suggests the community was fairly settled.

The bodies in Nataruk, in contrast, appeared to be part of a nomadic band of hunter-gatherers.

The archaeologists suggest two interpretations of their find. One was that the lakeshore area of West Turkana was so fertile and productive 10,000 years ago that it sustained a high population of hunter-gatherers, who were less nomadic and more materially wealthy than many such foraging groups. That would suggest warfare could still be a hallmark of fairly settled communities, but that hunter-gatherer communities could be more sedentary and populous than previously understood.

Alternately, they say, the discovery could indicate that warfare was a part of life for nomadic hunter-gatherers — that violent conflict between such groups might have been "ephemeral, but perhaps not unusual."

In that case, war wouldn't be a side effect of human settlement, but potentially a far older facet of human culture.

Study co-author Robert Foley said that doesn't have to be a wholly grim idea.

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