Atapuerca and the Sima de los Huesos: the pit of ancestors

In 1976, a team of Spanish speleologists and palaeontologists descended once more into a 19th-century railway cutting through the Sierra de AtapuercaAtapuercaA complex of archaeological sites in the Sierra de Atapuerca (Burgos, Spain), a UNESCO site, yielding an exceptional sequence of human fossils, including the Sima de los Huesos and Homo antecessor.→, fifteen kilometres east of Burgos. They did not yet know they were about to radically change our understanding of human evolution in Europe. Today, Atapuerca is the most important prehistoric site on the continent, inscribed on the UNESCO World Heritage List since 2000, and excavations are still ongoing¹.

An exceptional karstKarstA limestone landscape shaped by rock dissolution, rich in caves and passages; its sediments can preserve bone and DNA over long timespans.→ complex

The Sierra de Atapuerca is a limestone massif riddled with underground galleries that have acted as natural traps for millions of years. The railway cutting sliced through several of these galleries, exposing their fossil-bearing infills. The main sites are: Gran Dolina, where remains of Homo antecessor were found; Sima del Elefante, yielding the oldest hominins in Western Europe; and above all, the Sima de los HuesosSima de los HuesosA natural shaft at Atapuerca (Spain) that yielded over 6,500 bones of at least 29 Homo heidelbergensis individuals dated to −430,000: the largest Middle Pleistocene human fossil assemblage.→, a natural shaft at the bottom of which hundreds of human bones were accumulated under still-debated circumstances. The scientific directors, Eudald Carbonell, Juan Luis Arsuaga and José María Bermúdez de Castro, received the Prince of Asturias Award for Science in 1997².

Homo antecessor: the first European (−1.2 Ma)

In 1994, Gran Dolina yielded fossils dated to 800,000–1,200,000 years ago that matched no known human species. Their association with OldowanOldowanThe oldest known stone-tool industry (c. 3.3–1.7 Ma), characterised by flaked pebbles (choppers) and basic flakes. Named after Olduvai Gorge (Tanzania).→ tools and animal bones bearing butchery marks, including human bones, led the team to define a new species: Homo antecessor. Its face shows a striking modernity comparable to Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→, combined with a primitive braincase. Some researchers see it as a common ancestor of Neanderthals and modern humans; others link it to Homo erectus. The debate is open. So is the interpretation of the cut marks on the human bones, which indicate an episode of cannibalism, the oldest documented in Europe¹.

The Sima de los Huesos: a funerary pit 430,000 years old?

Five hundred metres from Gran Dolina, reached by crawling through a 30-metre gallery then descending a 13-metre shaft, the Sima de los Huesos is one of the most astonishing discoveries in world palaeoanthropologyPalaeoanthropologyThe science that studies human evolution from the fossil remains of hominins (bones, teeth, footprints) and their context, to reconstruct our biological origins.→. Since 1984, excavators have recovered over 6,500 bones belonging to at least 29 individuals, men, women, adolescents, children, dated to about 430,000 years ago. This is, by far, the largest assemblage of Middle PleistocenePleistoceneThe geological epoch of the great ice ages (c. 2.6 Ma–11,700 BP), spanning most of human prehistory.→ human fossils ever found.

These individuals belong to Homo heidelbergensis: robust, with brains of 1,100–1,400 cm³, pronounced brow ridges, but already close to the Neanderthals. Genetic analysis published in 2016 confirmed this kinship: their mitochondrial and nuclear DNA places them directly on the Neanderthal lineage, well before the split with the Denisovans. It is the oldest genomic sequence ever extracted from a European homininHomininMember of the subtribe Hominina, comprising the human lineage (Homo, Australopithecus, Paranthropus…) but excluding orangutans and gibbons. The term progressively replaces "hominid" in its narrow sense.→.

How did 29 individuals end up at the bottom of this shaft? The dominant hypothesis is intentional deposition of the dead, an organised funerary gesture at a time when such behaviour was thought impossible. A single non-bone object was found in the pit: a pink quartzite biface, named Excalibur, not from the immediate surroundings. Its presence is unexplained and fascinates researchers: an offering? a status symbol? sheer coincidence? We do not know².

Sima del Elefante: the oldest hominins in Western Europe

In 2008, Sima del Elefante yielded a jawbone and a few bones dated to 1.1–1.2 million years ago, the oldest human remains ever found in Western Europe. They were associated with rudimentary Oldowan tools and bones of horses, rhinoceroses and bears. These hominins, whose species remains uncertain, attest to a human presence in Europe far earlier than 20th-century scholarship believed.

Atapuerca today: a permanent dig

Excavations at Atapuerca continue every summer. Each campaign brings new fossils, new dates, new clues about the behaviour of these lost humanities. The Sierra has probably not yet revealed all its secrets: the karst networks remain largely unexplored, and each new gallery opened could hide a site as exceptional as the Sima de los Huesos. Atapuerca is not just a fossil site, it is a window onto 1.2 million years of human presence in Europe¹.