In Jurassic Park, scientists extract DNA from dinosaur blood found in mosquitoes preserved in amber, and use that DNA to re-create a Tyrannosaur. But dinosaur DNA would be at least 60 million years old, and until now no DNA has been found to have survived more than 100,000 years.
While we’re still nowhere near extracting dinosaur-age DNA, this week we learned that scientists have extracted 400,000-year-old DNA from a hominid thighbone. Moreover, what they’ve learned has changed their view of human evolution. What can we learn from really old DNA?
In the Atapuerca Mountains of Northern Spain, there lies an underground cave known as La Sima de los Huesos (“Pit of Bones.”) It’s an immensely rich source of hominid fossils, with more than 6,000 fossils from 28 separate ancient humans already unearthed. A study published in Nature this week describes the analysis of DNA drawn from a femur bone of one of these fossils.
The fossil bones look like those previously found in Neanderthals, but the DNA contained a surprise. Instead of being Neanderthal DNA, it resembled that drawn from fossils of a more recently identified and younger branch of humans, the Denisovans. Before the recent discovery, Denissovan DNA was only found in fossils located in Siberia, so its emergence at the Spanish site is forcing scientists to rethink how the branches of the human family tree merge together. They are now struggling to understand how Denisovan DNA showed up in bones at the Spanish site.
Our current notion about human evolution has divided our evolutionary lineage into three branches: Neanderthal, Denisovans and humans, with humans being the only surviving lineage. Some scientists think that the only real explanation for the “Pit of Bones” Denisovan discovery is that Denisovans and Neanderthals share a common, as yet unidentified, ancestor. If that’s true, it could mean that there are more than three, perhaps many more, branches to the human family tree and that they are more intertwined and extend to more corners of the world than originally thought.
Now that science can extract, examine and sequence DNA that is far older than any previously studied, we might have the tools to solve some of the mysteries of evolution we just uncovered.