Human Evolution More Complex: Oldest Human DNA Discovered

human evolution

Human evolution became more complex with the discovery of the oldest human DNA. The results of the DNA analysis conducted in a thigh bone extracted in Spain’s Sima de los Huesos or “pit of bones” have been released. The approximately 400,000 year old bone which came from an early human that roamed only in Europe also has a genetic material similar to those found in early humans that lived only in East Asia, according to researchers.

The analysis of the bones extracted from the Spanish cave sets a new record for the oldest human DNA sequence that was ever decoded. The discovery also challenges the conventional knowledge about how modern Homo sapiens’ ancient and extinct relatives spread around the world. Conventional thinking dictates that the Neanderthals exclusively resided only in prehistoric Europe while the Denisovans resided in what is today known as Siberia.

Researchers led by Matthias Meyer studying the DNA of the thigh bone from Spain’s “pit of bones” revealed that these early humans were actually closer in mitochondrial genome sequence to the Denisovans of Asia rather than that of the European Neanderthals.

Meyer, from Germany’s Max Planck Institute for Evolutionary Anthropology, said that the evolutionary history of both Denisovans and the Neanderthals may be more complicated than was previously thought, and that there is also the possibility that they interbred with other early human groups. Human evolution at this point, becomes more complex allowing  human DNA to incorporate into its genetic make-up characteristics of the different early human groups that were supposedly far removed from their locale.

Both Denisovans and Neanderthals walked the earth several thousands of years ahead of the modern-looking humans or Homo sapiens. The modern looking humans spread from Africa more than 60,000 years ago. The traces of the early humans’ genes, however small found in modern humans signifies that there was indeed interbreeding between these human groups. Previously, the oldest human bone that was DNA sequenced was less than 120,000 years old.

Many researchers and scientists are now asking how the DNA of early humans from Europe end up with the DNA of early humans from Siberia. The study, which was published in the journal Nature, posited some possible answers to this question of human evolution.

One possible scenario is that the Sima hominins are close relatives of the Denisovans and that they lived right alongside the Neanderthals. Another scenario is that the Sima hominins are actually an independent group that blended with the Denisovans and in the process passed their mitochondrial DNA. However, this scenario cannot explain why they also have traces of the Neanderthal DNA. Chris Stringer, an anthropologist from the Natural History Museum in London, suggested that the sexual encounters between these early human groups allowed the transmission and mixture of their individual DNA.

Meyer added that a full decoding of the genetic map or genome is needed in order to understand not only the mitochondrial DNA of the Sima hominins but also provide a strong evidence on the Sima hominins’ family history.

The thigh bone was pulled from a cold and damp tunnel 90 feet below from the surface of Spain’s northern Sierra de Atapuerco. The pit contains other fossilized bones belonging to a possible 28 individuals and is considered the world’s largest collection of human fossils coming from the Middle Pleistocene era (125,000 to 780,000 years ago).

The Denisovans existence was discovered in 2010 in Denisova Cave in the Altai Mountains of Siberia. Researchers and scientists studied a fragment of bone believed to come from a child’s finger and two teeth from the said cave in Siberia. According to Svante Paabo, a biologist at the Max Planck Institute,  one major characteristic of the Denisovans, based on limited evidence, is that they must have had large mouths because of the size of the teeth samples found.

Human evolution became more complex with the discovery of the oldest human DNA sequence through the thigh bone retrieved from the Sima pit. This just made the study of human evolution more exciting and “irritating”, added Meyer.

By Roberto I. Belda

National Geographic

Los Angeles Times

Yahoo News

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