There are lots of cold cases that have long eluded scientists, but now researchers may have found evidence of the world's oldest murder with puncture wounds in a prehistoric skull.

The skull, discovered among the skeletal remains of at least 28 individuals at the Sima de los Huesos site in northern Spain, date to around 430,000 years ago, during the Middle Pleistocene time period. The only access to the site is through a 13-meter (42-foot) deep vertical shaft, and how the human bodies arrived there remains unclear.

But the real mystery is that of a nearly complete skull, Cranium 17, which is composed of 52 cranial fragments recovered during excavations at the site over the last 20 years. Interestingly, this skull shows two penetrating lesions on the frontal bone, above the left eye.

"Evidence for interpersonal violence in the human fossil record is relatively scarce, and this would appear to represent the coldest cold case on record," anthropologist Rolf Quam of Binghamton University said in a news release.

Using modern forensic techniques, including contour and trajectory analysis of the traumas, Quam and his colleagues showed that both fractures were likely produced by two separate impacts by the same object, with slightly different trajectories around the time of the individual's death.

Based on the results, it is unlikely that the injuries were sustained from an accidental fall down the vertical shaft. Rather, due to the type of fracture, the location of the lethal wounds, and the fact that they appear to have been produced by two blows with the same object, the authors concluded that they were the result of what may be the earliest case of murder in human history.

Furthermore, if this individual was already dead, other humans likely carried them to the top of the vertical shaft. The findings suggest that humans were likely responsible for the accumulation of bodies in the Sima de los Huesos, which supports the idea that this site represents early evidence of funerary behavior.

"This is really good evidence for an intentional role for humans in the accumulation of bodies at the bottom of this pit and suggests the hominins from this time period were already engaging in complex cognitive behaviors," said Quam.

The skull and its lethal wounds are described in more detail in the journal PLOS ONE.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).