The Dirt on DNA
German scientists just made a major breakthrough in sequencing the DNA of our ancient ancestors. While researchers have long relied on painstaking work and pure good luck to uncover the fossilized remains of our predecessors, a new technique has allowed scientists to pull DNA from something far more abundant: dirt.
Scientists have understood for years that genetic material from a decomposing entity – whether animal, plant, or human — is released into the surrounding sediment and can remain there for a long time. The problem is there's a lot of it and it's all mixed up. Parsing out only human DNA deposits from even a tablespoon of dirt has traditionally been very difficult to do.
Led by Viviane Slon, scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have developed a process for retrieving and sequencing those DNA deposits, and they are now the first researchers to recover ancient human DNA directly from sediment. To do so, they created molecules that would target and extract DNA from mammals, specifically mitochondrial DNA, which is more abundant. The team presented its findings in the journal Science last week.
A New Kind of Discovery
Slon's team shines a new light on the Denisovans, a cousin to our Neanderthal ancestors that we know very little about. So far, scientists have only recovered a fossilized finger bone and a couple of teeth, both of which came from a single cave in Siberia. If the technique for analyzing DNA from dirt becomes a regular part of field work, there's the potential for discovering more evidence of this ancient ancestor in places without fossils. It will teach us more about what early humans were doing outside of the caves in which they lived (and apparently died), including migratory information.
For paleontologists and archeologists, the prospect of no longer having to rely quite so heavily on the exciting — but relatively rare — discovery of fossils will likely come as a relief. Even when they are able to find a fossil, putting it through the paces for sequencing can compromise its integrity as a specimen, making researchers no friend to museum curators or civilizations looking to preserve the remains of their ancient ancestors.
Perhaps most exciting of all, though, is the fact that being able to retrieve DNA in the absence of bones could add new branches to humanity's family tree, giving researchers insight into early humans that we have yet to find skeletal evidence of.