The discovery of two Neolithic skulls in a cave in southern Spain has given archaeologists a rare glimpse into the funerary rites of ancient Iberians some 6,000 years ago. Dated to between 4800 and 4200 BCE, the two severed craniums – which belonged to a male and an older female – were buried alongside the remains of a young goat, numerous stone tools, pieces of pottery, and a single human thumb bone.

The age of the bones is particularly important, as it places the burial in the Middle Neolithic, a period for which archaeological evidence is extremely rare in the Iberian Peninsula. In contrast, a wealth of artifacts and burials from both the Early and Late Neolithic periods have been excavated throughout what is now Spain and Portugal.

Unearthed at the Cueva de la Dehesilla in Cádiz, this latest find provides some fascinating new insights into the ritualistic behavior of the region’s ancient inhabitants. According to the researchers, the cut marks in the occipital bone of one of the skulls suggest that the head was removed from the body almost immediately after death, leading to the possibility that the act may have occurred as part of a human sacrifice.

Suggestions of a ritualistic killing are reinforced by the discovery of a stone alter next to the burial site, which may well have provided a platform for ceremonial offerings. The presence of a young goat, meanwhile, indicates that the burial may have taken place in spring, leading the study authors to speculate that the entire affair could have been part of a seasonal ritual of some sort.

Burnt cereal crops were also found within the grave, indicating that the skulls belonged to members of a sedentary community of agriculturalists – all of which could be seen to reinforce the notion of a seasonal offering.

"This finding opens new lines of research and anthropological scenarios, where human and animal sacrifice may have been related to ancestral cults, propitiatory rituals, and divine prayers in commemorative festivities," explained study author Daniel García Rivero in a statement.

Describing their discovery in the journal PLOS ONE, the researchers expand on this point by stating that "the deposit may indicate some type of honorary recognition, related to social leaders, perhaps great figures or religious guides."

As if all that weren’t fascinating enough, the female skull also appears to have undergone trepanation, which involves the opening of a small hole in the cranium. The fact that the bone had partially healed suggests that the woman in question was trepanned at some point while she was still alive, which may bear some relevance to her social or religious standing.

Clearly, much of the evidence recovered from the Cueva de la Dehesilla is open to interpretation, and the researchers can’t say with any certainty what this strange burial really says about Middle Neolithic Iberian life. Given the scarcity of archaeological finds from this period, though, this amazing discovery does at least provide an intriguing starting point from which to begin piecing together the funerary rites of this ancient population.