Human evolution theories may need to be revisited after archaeologists unearthed a 400,000-year-old human thigh bone which provides new valuable insight regarding human ancestry, BBC reports.
The ancient femur instead of providing answers to the origin of modern man instead poses more questions. It has become a complicated yet interesting subject of human evolution researchers.
The thigh bone or femur was unearthed from the popular and rich Spanish archaeological site, “the Pit of Bones,” or “Sima de los Huesos” in Spanish. There were about 28 ancient individuals from the Middle Pleistocene age that have already been found from the pit so far.
The archaeologists from the National Research Centre for Human Evolution (CENIEH) worked diligently to excavate the fossils from the narrow and dark cavities of the pit. They pieced together the sequence of mitochondrial DNA (mtDNA) of the femur almost completely. MtDNA is the genome sequence which can be found in the power resource of human cells.
The scientists were surprised at the results when they compared its genetic makeup to the modern humans. They were expecting to find a link between the Spanish fossils to Neanderthals because of the similarity in physical structures.
However, the mtDNA showed characteristics of Denisovans, a genetically distinct sister population of the Neanderthals. The Denisovan fossils which compose of a small finger bone and a tooth were found thousands of kilometers away from the pit, in Siberia’s Denisova Cave.
From a sequence of mutations of the ancient DNA, the researchers reckon that the ancient person from the Pit of Bones had common ancestry with the Denisovans, which goes as far back as 700,000 years.
Two theories were formulated to explain the presence of a similar Denisovan genetic makeup in Spain during the mid-Pleistocene age. One, the Pit of Bones mtDNA was from a common ancestor of the Denisovans and Spanish hominids. Two, the people from the Pit of Bones and another ancient human population interbred and took the Denisovan genetic makeup to the west.
According to co-author Professor Bermudez de Castro, a possible ancient species could fit this description, the Homo antecessor. The antecessor is an ancient human species which, a million years ago, roamed the Gran Dolina, a site just some hundred meters from the Pit of Bones.
Germany’s Max Planck Institute for Evolutionary Anthropology Director Svante Paabo, who supervised the researchers, said that the sequencing of nuclear genome “will answer definitively the question of how they are related to Neanderthals, modern humans and Denisovans."
Prof. Paabo, the institute's director, said: "Our results show that we can now study DNA from human ancestors that are hundreds of thousands of years old," adding: "It is tremendously exciting."
