Also among the discoveries was a man shot in the head with an arrow and appeared to have survived before being killed by a blow to the head. The arrow was still stuck in his skull, according to a Huffington Post report.
Two other men found among the remains also had stones that were lodged in their skull and thorax, indicating a brutal fight that did not end well for these individuals.
Researchers at Cambridge University said this wasn't a burial site, but the site of a slaughter. It was found in Nataruk near Lake Turkana.
It's the earliest known historical conflict uncovered by researchers. They were formally dated between 9,500 and 10,500 years old.
The fight was likely against prehistoric hunter-gatherers, and the victims were likely a small band of foragers.
The site was quite a find, as it included 12 complete skeletons, with 10 of them showing signs of a violent death. At least five had shown signs of being clubbed with blunt-force trauma to the head. One skull even showed trauma to both sides of the head.
The research team said the group was probably extended family or a tribe of foragers. It's not clear why they were attacked with such violence, but it was probably a robbery of resources like territory, women, and food.