Oldest human DNA found by scientists in Spain

Palaeontologists have extracted and decoded DNA from a hominid fossil dating back 400,000 years – the oldest human genetic material analysed by far.

A thigh bone found in the Sima de los Huesos (Pit of Bones) cave in northern Spain provided the DNA, which opens a route to studying the complex evolutionary relationships between ancient human species.

The researchers, from the Max Planck Institute for Evolutionary Anthropology in Leipzig and the Centre for Research on Human Evolution and Behaviour in Madrid, published their discovery in the journal Nature.

“Our results show that we can now study DNA from human ancestors that are hundreds of thousands of years old,” said Svante Pääbo, director of the Leipzig institute. “It is tremendously exciting.”

The Sima DNA comes from mitochondria, the biochemical power-packs that provide cells with their energy. Each cell has multiple copies of mitochondrial DNA, which is more likely than the main genome in the cell nucleus to survive in fossils. Mitochondrial DNA passes down the generations from mother to daughter.

When the researchers compared the Sima DNA with other humans, they were surprised to find that it most closely resembled mitochondrial DNA from Denisovans – a mysterious ancient group known only from a 50,000-year-old finger bone and two teeth discovered in a Siberian cave.

“The fact that the mitochondrial DNA of the Sima hominid shares a common ancestor with Denisovan rather than Neanderthal mitochondrial DNA is unexpected, since its skeletal remains carry Neanderthal-derived features,” said Matthias Meyer, the study leader.

Chris Stringer, of London’s Natural History Museum, and the leading UK expert on human origins, said he regarded the people living in northern Spain 400,000 years ago as early Neanderthals evolving from the previous ancestral species, Homo heidelbergensis, and not as ancestral Denisovans.

Our results show that we can now study DNA from human ancestors that are hundreds of thousands of years old

The most likely explanation for the DNA mystery is that both Denisovans and the Sima fossil carried mitochondrial gene sequences derived from Homo heidelbergensis, a common ancestor of Denisovans, Neanderthals and modern humans. These sequences would later have been lost by chance in ancestral modern humans and in Neanderthals, because the women carrying them had no surviving daughters, but survived in Denisovans and the Sima people.

There are also possibilities involving interbreeding between Homo heidelbergensis and another ancient human species or subspecies such as Homo antecessor.

“This unexpected result points to a complex pattern of evolution in the origin of Neanderthals and modern humans,” said Juan-Luis Arsuaga, director of the Centre for Research on Human Evolution and Behaviour. “I hope that more research will help clarify the genetic relationships of the hominids from Sima de los Huesos to Neanderthals and Denisovans.”

The researchers are now trying to retrieve genetic material from more Sima bones, including DNA from the main genome.