Skull 5 Homo heidelbergensis or related species 400,000 years old photo D. Finnin/AMNH

Most of the bones from Sima de los Huesos are extensively broken and fractured—including this skull. The individual fragments, however, survived the rigors of the burial process and researchers were able to reassemble them. The resulting Skull 5 is one the most exquisitely preserved fossil hominid skulls ever found anywhere in the world. Working from this specimen, scientists have been able to reconstruct what these early humans may have looked like.

The early humans who lived in the region of Atapuerca some 400,000 years ago represent a distinct species from the earlier Gran Dolina population. The scientists who discovered the Sima hominids have tentatively classified them as members of Homo heidelbergensis, named for Heidelberg, Germany, the first site where that species was found.

Evidence from other sites of similar age suggests that this species probably used throwing spears and built fires—two things for which there is so far no evidence at the Gran Dolina site. The early humans of Sima de los Huesos resembled the Neanderthals, a later species that eventually inhabited Europe and part of Asia before going extinct some 30,000 years ago. Indeed, some scholars have suggested that the species at Sima de los Huesos was a direct ancestor of the Neanderthals.

Numerous scars on Skull 5 indicate that during life, this individual, presumed to be male, survived several blows to the head. There is also evidence that one tooth broke off, leading to an infection that eventually proved fatal.