Scientists from the Max Planck Institute in Germany think they may be able to extract the DNA of a human ancestor who's been dead for tens of thousands of years from dirt collected from the floor of Denisova Cave in Siberia. If they're successful, it could open a new door into understanding these extinct relatives of humans.
     Most ancient DNA is extracted from bones or teeth, but researchers hate to destroy precious bones.
     Anthropologist Matthias Meyer says other scientists have recovered DNA from a variety of species in the floors of caves: "You just take a shovel with some dirt, and then you look for DNA." Meyer has some of this ancient human DNA from cave floors, and begun analysing it, but he'll have to develop methods to be certain that the DNA came from an ancient human bone, and not a more recent human cave explorer or contaminating bacteria.
     A colleague of Meyer's, Janet Kelso reveals that: "We've initiated a project just this year to try and generate sequences from a large number of Neanderthals, to try to understand something about the Neanderthal population histories." If archaeologists can get DNA samples from Neanderthals at various time points in their history, Kelso says, "we can see how were they adapting to the environment. How did they differ over time? Can we understand what happened to them in the end?"
     Another question is how often Neanderthals and modern humans interbred.
     Kelso says most modern human populations have at least some genetic connection to Neanderthals, but there are many questions about when and where Neanderthals made their contributions to the modern human gene pool.
     The answers may come from dirt on the floor of caves.

Edited from NPR (4 January 2017)