Most of the sites you can look at and get a rough sense of what’s going on, but this is one of those where it’s, like, I really don’t know. It’s a very strange site. There’s clearly something ritual going on here. What all that means, I don’t think we’ll ever know.

That’s how University of Notre Dame anthropologist Mark Golitko described the recent discovery of a strange Stone Age burial site in Sweden that has scientists baffled. The site is a grizzly display of ritual violence and mutilation that seems straight out of a classic splatter film. One mixed with Clan of the Cave Bear. The scene would have been horrific when it was still fresh: bashed-in heads with their lower jaws ripped off and impaled on stakes lying just below the water’s surface in a clear mountain lake. Piles of other skulls and bones lay strewn about those lucky enough to have earned a place on the stake, all on top of a flat stone platform composed of carefully placed individual small stones. What happened to these people some 8,000 years ago, and who left their heads on stakes in an elaborate underwater tomb?

In all, eleven adult individuals and an infant have been identified. Three of the adults were females, while six or seven are conclusively males. The most curious feature of all is the fact that all of the skulls show signs of horrific blunt force trauma. The females tended to have signs of multiple injuries on the backs of their heads, while the males all exhibited injuries towards the top and front. It’s possible these were members of some stigmatized and often abused group, or they could be the victims of the caveman form of gang violence. Interestingly, all of the skulls also showed signs of healing, implying this violence was a part of daily life – as well as death. Fredrik Hallgren, an archaeologist with Sweden’s Cultural Heritage Foundation calls it “a very enigmatic structure. We really don’t understand the reason why they did this and why they put it under water.”

The study of the site has been published in the journal Antiquity under the hilariously descriptive name “Keep your head high: skulls on stakes and cranial trauma in Mesolithic Sweden.” According to the article, some of the most likely explanations for the head trauma include “accidents, interpersonal violence, forced abduction, spousal abuse, socially regulated nonlethal violence, or warfare.” Classic images of cavemen bashing women in heads with clubs and dragging them away by their hair aside, I’m more interested in the “socially regulated nonlethal violence.” Does that mean some sort of punishment ceremony or violent ritual where cavepeople got their heads smashed in by a rock in front of a willing audience? Yuck. Although is that really too different from the NFL?