One of the Sima de los Huesos skeletons
One of the Sima de los Huesos skeletons. Image: Credit: Javier Trueba, Madrid Scientific Films

The genome of the oldest human DNA ever has just been sequenced.  The DNA was taken from a thigh bone and tooth of a 430,000 year old skeleton found in Spain’s Sima de los Huesos or “pit of bones.”

A team of German researchers found evidence that modern humans split from Neanderthals hundreds of thousands of years earlier than we thought.  It might be time to redraw the family tree.

The Sima de los Huesos archaeological site is part of the Cueva Mayor-Cueva del Silo cave system in north-central spain.  It contains the largest and oldest collection of human remains ever discovered.  More than 6,500 fossilised bone fragments from at least 28 different hominins have been discovered so far.

Some remains date back to 430,000 years ago which is allowing scientists to use the “pit of bones” to reconstruct the human family tree far beyond the past 100,000 years, bringing the current human family tree into question.

One of the Sima de los Huesos skeletons
One of the Sima de los Huesos skeletons. Image: Credit: Javier Trueba, Madrid Scientific Films

“It’s fascinating and keeps us all on our toes trying to make sense of it all,” palaeoanthropologist Chris Stringer from the Natural History Museum in London, who wasn’t involved in the research, told Nature Magazine. “Instead of just being stuck with trying to resolve the last 100,000 years, we can really start to put some dates from DNA further down the human tree.”

Previously the bones found in Sima de los Huesos were attributed to early ancestors of the Neanderthals.

But sequencing of the mitochondrial genome of a femur found in the pit showed that it is more closely related to the Denisovans, an extinct species of human that had previously been found in Siberia.

This finding had had two major implications:

  1. At least one individual buried in the pit was not directly related to the Neanderthals.
  2. At least one individual buried in the pit was directly related to the Denisovans even though Denisovans were not thought to have existed for at least another 100,000 years.

This is yet another clue to understanding who the Sima hominins were.  They are perplexing because they show similarities to Neanderthals yet also appear to be connected to ancient humans.

Ewen Callaway from Nature Magazine explains:

“The Sima hominin skulls have the beginnings of a prominent brow ridge, as well as other traits typical of Neanderthals. But other features, and uncertainties around their age – some studies put them at 600,000 years old, others closer to 400,000 – convinced many researchers that they might instead belong to an older species known as Homo heidelbergensis.

The German researchers that sequenced the nuclear and mitochondrial DNA wanted to show clear evidence of how the skeletons in the “pit of bones” fit into our evolutionary tree.

They found that most of the 430,000 year-old DNA was degraded beyond use, the parts of the genome that they were able to decode showed that these individuals were early Neanderthals.

This means that we have direct evidence of Denisovans and Neanderthals at the same place in the same moment in time.  It indicates that both of these groups evolved from a common ancestor 430,000 years ago, way earlier than anyone thought.

“We know that Denisovans and Neanderthals shared a common ancestor that had split from our modern human lineage. In light of the new nuclear DNA evidence, Meyer’s team suggests this split might have happened as early as 765,000 years ago. Previous DNA studies had dated this split to just 315,000 to 540,000 years ago, says Katerina Harvati-Papatheodorou at the University of Tubingen in Germany.”