Archaeologists in Sweden have uncovered mysterious 8,000-year-old skulls mounted on wooden stakes that shed new light on grisly Stone Age rituals.

Gruesome: skulls found impaled on stakes

Excavations at Kanaljorden in southern Sweden revealed the remains of at least 10 people – nine adults and one fetus or infant. Relatively complete crania were found for the adult remains, two of which were identified as female and four as male. An almost complete skeleton was found for the infant, according to experts from the University of Stockholm and Sweden’s Cultural Heritage Foundation.

Chillingly, the remains of wooden stakes were recovered inside two of the adult crania, indicating that they had once been mounted.

The gruesome finds, which were uncovered at the site of a former lake, are described in an article titled “Keep your head high” in the journal Antiquity. “This unique site challenges our understanding of the handling of the dead during the European Mesolithic [period],” explained the authors of the study.

A smashed cranium and a wooden stake (Photograph: Fredrik Hallgren)

The Mesolithic Period is also known as the “Middle Stone Age.

The human remains and wooden stakes were discovered among a densely packed layer of large stones during excavations at Kanaljorden between 2009 and 2013. Animal remains, as well as stone, bone and antler tools, also were uncovered.

Experts believe that the stones once formed part of an unusual man-made ‘island’-type structure in the lake. “The discovery of selected remains of ten Mesolithic individuals deposited on a man-made stone structure underwater is unique,” they explain. “Additionally, 400 intact and fragmentary wooden stakes were recovered, some of which may similarly have been used to mount objects (e.g. skulls, animal remains or artifacts).”

Gruesome: skulls found impaled on stakes

Examples of blunt force trauma on the skulls discovered at Kanaljorden. (Photograph: Sara Gummesson and Fredrik Hallgren/Antiquity)

Bizarrely, most of the skulls show evidence of “healed blunt force trauma” although the nature of the blows differs by gender. “We have recognized a sex-related, non-random, trauma pattern, where non-lethal forces were directed to the back of the head of women and to the top of the head of men,” according to the study.

The puzzling wounds have prompted speculation that the victims may been slaves, although historians have noted that slavery was rare among the mobile Scandinavian hunter-gatherers of that era. Another possibility is that the injuries are the result of raiding and warfare, with the genders performing different combat roles. The same gender-related injuries, for example, have been noted among prehistoric hunter-gatherers in North America, according to experts.

Gruesome: skulls found impaled on stakes

The wounds also may have been a source of status or inflicted as part of a religious ritual.

Archaeologists are unable to establish the cause of death for any of the individuals.

Other archaeological projects have also been making macabre discoveries in recent years. Archaeologists in Mexico, for example, recently discovered an interlocked spiral of ancient skeletons. Last year archaeologists in Turkey revealed that human skulls may have once decorated an ancient temple.

A carved human bone from an archaeological dig in the U.K. is also offering new insight into the grisly culture of prehistoric cannibals.

More Fox News Headlines