The world’s oldest DNA found from a collection of bones in Spain could help write the history of early humankind. The research, published in the journal Nature, focuses on hominins from the Sima de los Huesos (“pit of bones”) site in Spain, according to Christian Science Monitor.
The site was found back in the ’90s, but scientists haven’t settled on their genetic origin. Now, by managing to extract some truly ancient nuclear DNA, researchers believe they’ve shown that the 430,000-year-old bones belonged to Neanderthal ancestors, or at least very close relatives.
That’s not an entirely new idea. A recent study pointed out striking physiological similarities between these Sima hominins and Neanderthals, our close cousins.
While the world’s oldest DNA found is exciting, researchers explain how they come to that conclusion. Neanderthals only emerged about 40,000 years ago, but researchers suggested that the 28 hominins found in the pit of bones might belong to the species Homo heidelbergensis, which lived in the right place and time and was thought to be an ancestor of Neanderthals.
Then the plot thickened: DNA analysis published in 2013 suggested that the Sima hominins were actually more closely related to Denisovans — a less understood lineage of human.
But this isn’t just another he-said-she-said of the oldest DNA tale. The 2013 study analyzed mitochondrial DNA (mtDNA), which is easier to recover from ancient bones. But it doesn’t tell the whole story of this oldest generation. It’s a small molecule of DNA found in the mitochondria of each cell — the cell’s power plant. When an egg and a sperm meet, only the egg cell holds onto its mtDNA — so while a person’s nuclear DNA will paint a unique portrait of their genetic lineage, mtDNA extracted from the same individual will show an identical copy made straight down the maternal line, save for any mutations that have been picked up along the way.
While the new study confirms that the Sima hominins really do have mtDNA that loops them in with the Denisovans, it also shows that the nuclear DNA is consistent with that you’d find in a Neanderthal ancestor.
The DNA results suggest that Neanderthals and Denisovans diverged a good 400,000 years back, giving the Sima lineage time to pick up a new set of mtDNA as the generations went on — one that would match Neanderthals as we know them to be the oldest in history.
And based on the oldest DNA analysis, the researchers believe that Neanderthals and Homo Sapiens may have split from their last common ancestor more than 600,000 years ago, which is a few hundred thousand years earlier than previously assumed.
“Research must now refocus on fossils from 400,000 to 800,000 years ago to determine which ones might actually lie on the respective ancestral lineages of Neanderthals, Denisovans and modern humans,” Chris Stringer of the Natural History Museum in London, who wasn’t involved in the oldest DNA study.
In other words, the world’s oldest DNA found study poses more questions than it answers. Theories on the early days and interwoven family ties of humanity — already poorly understood — might be in need of a major overhaul. But while these proto-Neanderthals may have scientists scratching their heads for some time, the analysis of their long-sought DNA shows how far scientific techniques have come in just a few decades.