Scientists have extracted and decoded the oldest human DNA from a fossilised leg bone of an early human who died about 400,000 years ago in what is now Spain.
Using novel techniques researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, determined an almost complete mitochondrial genome sequence of a 400,000-year-old representative of the genus Homo from Sima de los Huesos, a unique cave site in Northern Spain.
Researchers found that it is related to the mitochondrial genome of Denisovans, extinct relatives of Neanderthals in Asia.
DNA this old has until recently been retrieved only from the permafrost, researchers said.
Sima de los Huesos (SH), the "bone pit", is a cave site in Northern Spain that has yielded the world's largest assembly of Middle Pleistocene hominin fossils, consisting of at least 28 skeletons, which have been excavated and pieced together over the course of more than two decades by a Spanish team of paleontologists led by Juan-Luis Arsuaga.
The fossils are classified as Homo heidelbergensis but also carry traits typical of Neanderthals. Until now it had not been possible to study the DNA of these unique hominins.
Researcher Matthias Meyer and colleagues developed new techniques for retrieving and sequencing highly degraded ancient DNA, 'Phys.org' reported.
They then joined forces with Juan-Luis Arsuaga and applied the new techniques to a cave bear from the Sima de los Huesos site.
Researchers sampled two grammes of bone powder from a hominin thigh bone from the cave. They extracted its DNA and sequenced the genome of the mitochondria or mtDNA, a small part of the genome that is passed down along the maternal line and occurs in many copies per cell.
They then compared this ancient mitochondrial DNA with Neanderthals, Denisovans, present-day humans, and apes.
"The fact that the mtDNA of the Sima de los Huesos hominin shares a common ancestor with Denisovan rather than Neanderthal mtDNAs is unexpected since its skeletal remains carry Neanderthal-derived features," said Meyer.