Sima de los Huesos, or the “Pit of Bones,” is a significant archaeological site located in the Atapuerca Mountains in northern Spain, near the town of Ibeas de Juarros, in the Burgos Province.
The site has provided one of the most important insights into the early history of humanity, with its discovery and excavation revealing secrets about our distant ancestors.
The discovery of Sima de los Huesos dates back to 1976 when a team of researchers led by Spanish archaeologist Emiliano Aguirre was conducting excavations in the Atapuerca region.
Aguirre and his team were exploring the area for signs of early human occupation when they stumbled upon an unusual feature of the landscape—a deep, vertical shaft, which appeared to have been filled with bones.
This was the Sima de los Huesos, and it quickly became one of the most extraordinary sites for the study of human prehistory.
The site was discovered by accident when the team was investigating a different part of the Atapuerca caves. The pit, located in the Cueva de los Huesos (Cave of Bones), was initially found when archaeologists noticed a large number of animal bones scattered at the entrance of the cave, with some human bones mixed in. Upon further excavation, it became clear that the cave contained a mass deposit of human remains.
The site is significant because it offers a remarkable snapshot of human evolution and evidence of a species known as Homo heidelbergensis, an extinct hominin species that lived approximately 400,000 to 600,000 years ago. These individuals are considered to be a key link between earlier species like Homo erectus and later species like Neanderthals and modern humans.
The bones found in Sima de los Huesos are primarily those of Homo heidelbergensis, though other animal remains were also found within the cave: the remains of at least 28 individuals, with some estimates suggesting as many as 40 individuals could be represented. This includes a mix of both adults and children, a treasure trove for researchers as it offers a broad view of the population at the time. Some of the bones appear to be from a single individual, while others show evidence of being moved or disturbed, indicating possible rituals or funerary practices.
The bones are often found disarticulated—separated into their individual parts—but are densely packed into the pit. Their condition and the way they are situated have sparked much debate and intrigue among scientists.
In addition to the human remains, the site also contains bones from a variety of animals, including bears, deer, and wild boars. Tools and other artefacts have not been found within the pit itself, but nearby caves in the region have yielded evidence of stone tools used by Homo heidelbergensis.
Perhaps most interestingly, the bones of Homo heidelbergensis found in the pit show signs of trauma and injuries, with some individuals showing evidence of healed fractures, suggesting that these early humans were capable of survival and adaptation despite the challenges they faced.
The exact reason why so many human bones ended up in the pit is not fully understood, but there are several prevailing theories. One is a natural accumulation which speculates that the pit simply served as a natural trap, where the bones of humans and animals accumulated over time. The deep, narrow shaft would have acted like a funnel, with bodies falling into the pit, whether through accident or intentional action.
Another, and perhaps the most interesting, hints at some sort of ritualistic behaviour, suggesting that the pit served a symbolic or ritualistic purpose for the humans of the time. Some scholars argue that the repeated deposition of human remains in this deep, dark pit suggests that early Homo heidelbergensis may have engaged in ritualistic or ceremonial behaviours, possibly viewing the pit as a sacred place or a burial site.
A third theory posits that Homo heidelbergensis may have used the cave as a place of shelter, and when individuals died, their bodies could have been thrown into the pit. In this case, the pit would serve not only as a natural death trap but also as a place where the remains of those who lived in the cave were discarded.
The discovery of Sima de los Huesos has provided valuable insights into the life and practices of Homo heidelbergensis, a species considered to be a direct ancestor of both Neanderthals and modern humans. In particular, the site has helped researchers understand the biological diversity of human ancestors during this period and provided evidence of behaviours that were previously thought to be exclusive to later human species.
The site has also shed light on the development of human cognitive abilities given that some of the bones show signs of careful handling. It is possible that the humans who deposited the bodies had some form of social structure or belief system.
Excavations at Sima de los Huesos continue to this day, with researchers from various institutions studying the site and analysing the remains. Over the years, more and more bones have been uncovered, as well as significant pieces of evidence relating to early human life. Among the notable discoveries was the finding of Neanderthal-like traits in some of the bones, suggesting a closer connection between Homo heidelbergensis and Neanderthals than previously understood.
In addition to bones, recent discoveries at the site include stone tools that provide insight into the technological capabilities of Homo heidelbergensis. DNA extraction from the bones has also led to groundbreaking findings about the genetic relationship between early hominins, with studies revealing that Homo heidelbergensis contributed to the genetic lineage of Neanderthals.
