The DNA of a 400 thousand year old hominid that confuses scientists
Analyzes carried out on fossil bones dating back 400 thousand years ago establish the new antiquity record for human DNA that has never been codified, and force us to question the theories regarding our distant ancestors.
A fossil femur found in the cave of Sima de los Huesos, in northern Spain, and which belonged to one of our ancestor who lived 400 thousand years ago, has made it possible to recover the oldest almost complete DNA of a hominid, revealing an unexpected link between hominids Europeans and the Denisovans, a mysterious population that lived much more recently in southwestern Siberia.
The genetic analysis puzzled researchers as most believed the site's inhabitants were evolutionarily closer to Neanderthals than Denisovans.
The fossil femur was excavated in 1990 from a deep cave at the extensively studied site of Sima de los Huesos (Bone Pit). The bone and the remains of more than two dozen other individuals found at the site had been attributed to both early Neanderthals, who lived in Europe until about 30,000 years ago, and Homo Heidelbergensis, a population of hominids little known, which is believed to have given rise to Neanderthals in Europe and perhaps to humans in Africa.
According to a 2013 publication (https://www.nature.com/articles/504016a), the bones previously thought to be Neanderthal are actually genetically close to Denisovans, as demonstrated by the mitochondrial DNA (transmitted maternally) extracted from the femur. Genetic analyzes of this ancient genetic material raise a new question about humanity's intricate past: how is it possible that an ancient human species in Spain possessed Siberian DNA?
Analysis suggests that Neanderthals and Denisovans had a common ancestor who lived up to 700,000 years ago. The Sima de los Hueos hominids may represent a founding population that once lived across Eurasia and then gave rise to two distinct groups. Both could carry the same mitochondrial sequence observed in the cave bones.
Another possibility, suggested by the anthropologist Chris Stringer of the Natural History Museum in London, is that the mitochondrial DNA of the Spanish human group reached the Denisovans thanks to sexual intercourse entertained by a third human group which would have transmitted the genetic material both to the inhabitants of Sima de los Huesos than to the Denisovans. Not far from the cave, in fact, researchers have discovered the bones of hominids who lived about 800 thousand years ago and which have been attributed to an archaic hominid called Homo Antecessor, perhaps a descendant of Homo Erectus.
But the Sima hominids could also belong to a completely independent group, which mixed with the Denisovans and passed on their mitochondrial DNA; however, this would not explain the Neanderthal features of those fossil remains. In any case, the identity of this ancient human group remains a mystery that can only be solved through further research.
A complex story
So far, the oldest human DNA sequenced came from bones less than 120,000 years old. In recent years, paleogeneticists have made surprising discoveries about ancient species of the Homo genus, especially regarding interbreeding between Neanderthals, Denisovans and H. Sapiens.
The Denisovans, discovered only in 2010, are known only thanks to a little finger bone and a tooth found in a rocky layer dated 30 thousand to 50 thousand years old inside the Denisova Cave, in Siberia. Genetic analyzes conducted on these bones revealed that the remains belonged to a group genetically different from both Neanderthals and modern humans.
Neanderthals and Denisovans appeared hundreds of thousands of years before anatomically modern humans, or Homo Sapiens, began spreading from Africa over 60,000 years ago. The small traces of their genes, found in recent years in our species, are the sign of interbreeding between ancient human groups.
The Atapuerca mountains, where the fossil remains were found, are a famous fossil site located in northern Spain: some of the oldest human remains were discovered in Western Europe. The most famous cave of this mountain group is Sima de los Huesos: it contains over 6,000 fossil finds belonging to 28 individuals who lived approximately 400,000 years ago. The exact origin of this pile of bones has not yet been clarified.
Is this accumulation of remains due to a natural catastrophe or the activity of predators?
Or perhaps it was those ancient men who piled up the bodies of their relatives and friends in this pit inside a dark, secluded cave?
