Ancient DNA from "Pit of Bones" sequenced

Deep within the Atapuerca Mountains of northern Spain lies an ancient cave known as Sima de los Huesos – in English, the Pit of Bones. The cave gets its name from the large number of prehistoric human remains discovered there over the years, which have made it one of the most important paleontological sites on the planet. Dozens of complete skeletons have been excavated thus far, and their analysis has helped researchers better understand the way modern humans – or Homo sapiens – evolved. 

Where exactly these bones fit into our family tree has, however, been the subject of much debate. Some believe that the fossils belong to the species Homo heidelbergensis – an ancient ancestor of Homo sapiens estimated to have walked the Earth around half a million years ago. Others argue that the bones are more recent than that, and are in fact the remains of one of Homo sapiens’ closest relatives, the Neanderthal. 

Now, DNA has been successfully extracted from a 400,000-year-old femur found at Sima de Los Huesos – by far the oldest human DNA ever sequenced. But far from clarifying things, the development has thrown up mysteries of its own.  When the DNA was compared to other DNA samples, the researchers were surprised to find a close similarity not with Neanderthal, as expected, but with another type of early human called the Denisovans – a separate lineage only discovered in 2008 through analysis of fossils unearthed in Siberia. Since there is no evidence to suggest that Denisovans existed outside of Asia, this revelation has forced experts to revise their theories as to how and when different species of early human arose. The researchers responsible for this discovery hope that further advances in DNA sequencing techniques will allow more fossils to be examined in this way, gradually building a complete picture of who we are and where we came from.