The findings of an analysis of 17 human skulls found in the Atapuerca hill in northern Spain have been released. The bones are believed to be about 430,000 years old.
The Sima de los Huesos (Pit of the Bones), where the skulls were found, have undergone excavation for the past 40 years, a Centro Mixto UCM-ISCIII de Evolución y Comportamiento Humano news release reported.
The site is difficult to access, and most samples taken from it are in small fragments and must be patiently reconstructed.
It is estimate that about 30 individuals have been recovered from the site. The researchers are working to determine why so many bodies ended up at the site.
No other site has turned over so many skulls of an extinct human species before.
The Sima population (which is found at the site) is believed to evolutionarily similar Neanderthals, and are the first to show clear Neanderthals features in the skull.
Studying the Sima skull could help researchers gain insight into the evolution of the human skull. The first changes are believed to have occurred in the "teeth, jaw and face," the news release reported. Other parts of the skull such as the cranial vault, or neurocranium, started to change further down the road.
One of the study's most important findings was the homogeneity of the Sima fossils taken from the site. All of the ancient individuals were from the same biological population. This means that researchers can study individual variation in the skeletons.
The Sima fossils have not been assigned to a specific species at this time, but they do have genetic differences from Neanderthals. This suggests the Sima are not just "early Neanderthals" and are also not members of the species known as Homo heidelbergensis due to their distinct jawbones.
"This is one of the outstanding questions and one that is sure to inspire considerable debate and controversy within the field. With excavations continuing and new fossils being discovered each field season, there is certainly reason to believe that the Sima de los Huesos will yield more surprising findings in the future," the news release reported.
