March 15, 2016

Human DNA from Spain’s ‘pit of bones’ details origin of Neanderthals

Thanks to a painstaking process, researchers have identified the oldest human DNA ever found.

According to a study published in the journal Nature, the DNA was actually from a pre-Neanderthal lineage that lived about 400,000 years ago.

The DNA was extracted from bones discovered in a cave in northern Spain known as the "Pit of Bones".

In making their discovery, the study team was only able to decode just 0.1 percent of the ancient genome. The specimens were severely degraded and contaminated and that meant researchers scrapped enough raw data to sequence our genome dozens of times over.

Learning more about our past through genetics

Despite the lack of genetic data, research found enough to reveal some evolutionary traits.

Using skeletal evidence, past research efforts had concluded the 28 people buried in the 42-foot-deep cave shaft belonged to a human species know as Homo heidelbergensis, a precursor to the classic Neanderthal.

The skeleton of an early neanderthal Credit: Javier Trueba, MADRID SCIENTIFIC FILMS

The skeleton of an early neanderthal Credit: Javier Trueba, MADRID SCIENTIFIC FILMS

However, a team reported in 2013 on mitochondrial DNA recovered from remains at the archaeological location, referred to as "Sima de los Huesos" in Spanish. Passed down only through the maternal line, the mtDNA revealed that the primates were in fact more closely related to Denisovans, ancient humans who lived in Asia more than 50,000 years ago.

This latest study, based on an analysis of DNA from the cell nucleus, disputes that 2013 finding.

“It’s wonderful news to have mitochondrial and nuclear DNA from something that is 430,000 years old. It’s like science fiction. It’s an amazing opportunity,” Maria Martinón-Torres, a paleoanthropologist at University College London whose work the study referenced, told Nature News.

The study team was able to obtain nuclear and mitochondrial DNA from five cave specimens, most likely representing several individuals. A crucial factor in their success was the careful refrigeration of teeth  and shoulder-blade tissue from the pit that has preserved the DNA since 2006, the researchers said.

In addition to confirming that these individuals are in fact early Neanderthals, the researchers also confirmed this species likely split from Neanderthals between 550,000 and 765,000 years ago – too far back for the shared ancestors to have been Homo heidelbergensis.

The team said they should now be on the lookout for a population that lived around 700,000 to 900,000 years ago, with a species known as Homo antecessor being the strongest candidate.


Pictured is bone powder used to sequence the genome. Image credit: Javier Trueba, MADRID SCIENTIFIC FILMS