Previous analyses of the hominins from Sima de los Huesos, a cave site in the Sierra Atapuerca in the north of Spain, showed that their mitochondrial DNA was distantly related to Denisovans, extinct relatives of Neanderthals in Asia. This was unexpected since their skeletal remains carry Neanderthal-derived features. Researchers have since worked on sequencing nuclear DNA from fossils from the cave. The results show that the Sima de los Huesos hominins were indeed early Neanderthals.
     Until now it has been unclear how the 28 individuals found at Sima de los Huesos were related to Neanderthals and Denisovans.
     "Sima de los Huesos is currently the only non-permafrost site that allow us to study DNA sequences from the Middle Pleistocene, the time period preceding 125,000 years ago", says Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology.
     Juan-Luis Arsuaga of the Complutense University in Madrid, Spain, who has led the excavations at Sima de los Huesos for three decades, says: "We have hoped for many years that advances in molecular analysis techniques would one day aid our investigation of this unique assembly of fossils."
     The nuclear DNA sequences recovered from two specimens show that they belong to the Neanderthal evolutionary lineage and are more closely related to Neanderthals than to Denisovans. This finding indicates that the population divergence between Denisovans and Neanderthals had already occurred when the Sima de los Huesos hominins lived.
     According to Svante Paabo of the Max Planck Institute for Evolutionary Anthropology "these results provide important anchor points in the timeline of human evolution. They are consistent with a rather early divergence of 550,000 to 750,000 years ago of the modern human lineage from archaic humans".
     Consistent with the previous study, the mitochondrial DNA of the Sima de los Huesos hominins is more closely related to Denisovans than Neanderthals. Mitochondrial DNA seen in Late Pleistocene Neanderthals may thus have been acquired by them later in their history, perhaps as a result of gene flow from Africa.

Edited from Max-Planck-Gesellschaft (14 March 2016)